# Wikipedia:Manual of Style/Dates and numbers

https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers

This page guides the presentation of numbers, dates, times, measurements, currencies, coordinates, and similar items in articles. The aim is to promote clarity, cohesion, and consistency, and to make the encyclopedia easier and more intuitive to use.

Where this manual gives options, maintain consistency within an article unless there is a good reason to do otherwise. The Arbitration Committee has ruled that editors should not change an article from one guideline-defined style to another without a substantial reason unrelated to mere choice of style; revert-warring over optional styles is unacceptable. [a] If discussion fails to resolve the question of which style to use in an article, defer to the style used by the first major contributor.

## General notes

### Quotations, titles, etc.

Quotations, titles of books and articles, and similar "imported" text should be faithfully reproduced, even if they use formats or units inconsistent with these guidelines or with other formats in the same article. If necessary, clarify via [bracketed interpolation], article text, or footnotes.

### Non-breaking spaces

Guidance on the use of non-breaking spaces ("hard spaces") is given in some sections below, but not all situations in which hard spaces ({{ nbsp}} or &nbsp;) or {{ nowrap}} may be appropriate are described. For further information see Wikipedia:Manual of Style § Non-breaking spaces and Wikipedia:Line-break handling.

## Chronological items

### Statements likely to become outdated

Except on pages updated regularly (e.g. the "Current events" portal), terms such as now, currently, to date, so far, soon, and recently should usually be avoided in favor of phrases such as during the 2010s, since 2010, and in August 2020. For current and future events, use phrases like as of October 2021 or since the beginning of 2021 to signal the time-dependence of the information; use the template {{ as of}} in conjunction.

Relative-time expressions are acceptable for very long periods, such as geological epochs: Humans diverged from other primates long ago, but only recently developed state legislatures.

### Dates, months, and years

#### Formats

Acceptable date formats
General use Only in limited situations
where brevity is helpful
[b]
2 September 2001 2 Sep 2001
September 2, 2001 Sep 2, 2001 A comma follows the year unless followed by other punctuation that replaces the comma:
• The weather on March 12, 2005, was clear and warm
• Everyone remembers July 20, 1969 – when humans first landed on the Moon
2 September 2 Sep Omit year only where there is no risk of ambiguity:
• The 2012 London Olympics ran from 25 July to 12 September
• January 1 is New Year's Day
September 2 Sep 2
No equivalent for general use 2001-09-02 Use yyyy-mm-dd format only with Gregorian dates from 1583 onward. [c]
September 2001 Sep 2001

• Dates, years, and other chronological items should be linked only when they are relevant to the subject and likely to be useful to a reader; this rule does not apply to articles that are explicitly on a chronological item, e.g. 2002, 19th century (as discussed at Wikipedia:Linking § Chronological items). [d]
• For issues related to dates in sortable tables, and , or consider using {{ dts|Nov 1, 2008}}.
• Phrases such as (or July Fourth, but not July 4th), , , and are proper names, to which rules for dates do not apply (A typical Fourth of July celebration includes fireworks).

Unacceptable date formats (except in external titles and quotes)
Sep. 2 Sep 2 [b] Do not add a dot to the day or to an abbreviated month. [e]
9. June 9 June or June 9
9 june
june 9
Months are capitalized.
9th June
June 9th
the 9th of June
Do not use ordinals (1st, 2nd, 3rd, etc.).
09-06
06-09
Do not use these formats.
09 June
June 09
Do not zero-pad day ...
2007-4-15 2007-04-15 [b] ... except in all-numeric (yyyy-mm-dd) format, where both month and day should be zero-padded to two digits.
2007/04/15 Do not use separators other than hyphens.
07-04-15 Do not abbreviate year to two digits.
15-04-2007
04-15-2007
2007-15-04
Do not use dd-mm-yyyy, mm-dd-yyyy or yyyy-dd-mm formats. [f]
2007 April 15
2007 Apr 15
Do not use these formats.
7/2001
7-2001
07-2001
2001-07
2001 July
July of 2001
July 2001 Do not use these formats.
July, 2001 No comma between month and year.
3 July, 2001 3 July 2001
July 3 2001 July 3, 2001 Comma required between day and year.
the '97 elections
the 97 elections
the 1997 elections Do not abbreviate year.
Copyright MMII Copyright 2002 Roman numerals are not normally used for dates.
Two thousand one 2001 Years and days of the month are not normally written in words.
the first of May
May the first
May 1 or 1 May
June 0622 June 622 Do not zero-pad years.
sold in the year 1995 sold in 1995 Write "the year" only where needed for clarity (About 1800 ships arrived in the year 1801).
##### Consistency

• Dates in article body text should all use the same format: She fell ill on 25 June 2005 and died on 28 June, not She fell ill on 25 June 2005 and died on June 28.
• Publication dates in an article's citations should all use the same format, which may be:
• the format used in the article body text,
• an abbreviated format from the "Acceptable date formats" table, provided the day and month elements are in the same order as in dates in the article body, or
• the format expected in the citation style being used (but all-numeric date formats other than yyyy-mm-dd must still be avoided).
For example, publication dates within a single article might be in one, but only one, of these formats (among others):
Jones, J. (20 September 2008)
Jones, J. (September 20, 2008)
• Access and archive dates in an article's citations should all use the same format, which may be:
• the format used for publication dates in the article (see above);
• the format expected in the citation style adopted in the article; or
• yyyy-mm-dd
For example, access/archive dates within a single article might be in one, but only one, of these formats (among others):
Jones, J. (September 20, 2008) ... Retrieved February 5, 2009.
Jones, J. (20 Sep 2008) ... Retrieved 5 Feb 2009.
Jones, J. (20 September 2008) ... Retrieved 2009-02-05.
When a citation style does not expect differing date formats, it is permissible to normalize publication dates to the article body text date format, and/or access/archive dates to either, with date consistency being preferred.
##### Strong national ties to a topic

For any given article, the choice of date format and the choice of national variety of English (see Wikipedia:Manual of Style § Strong national ties to a topic) are independent issues.

• Articles on topics with strong ties to a particular English-speaking country should generally use the date format most commonly used in that nation. For the United States this is (for example) July 4, 1976; for most other English-speaking countries it is 4 July 1976.
• Articles related to Canada may use either format with (as always) consistency within each article. (see Retaining existing format)
• In topics where a date format that differs from the usual national one is in customary usage, that format should be used for related articles: for example, articles on the modern US military, including biographical articles related to the modern US military, should use day-before-month, in accordance with US military usage.
##### Retaining existing format
• If an article has evolved using predominantly one date format, this format should be used throughout the article, unless there are reasons for changing it based on strong national ties to the topic or consensus on the article's talk page.
• The date format chosen in the first major contribution in the early stages of an article (i.e., the first non-stub version) should continue to be used, unless there is reason to change it based on strong national ties to the topic or consensus on the article's talk page.
• Where an article has shown no clear sign of which format is used, the first person to insert a date is equivalent to "the first major contributor".

#### Era style

• The default calendar eras are Anno Domini (BC and AD) and Common Era (BCE and CE). Either convention may be appropriate for use in Wikipedia articles depending on the article context. Apply Wikipedia:Manual of Style § Retaining existing styles with regard to changes from one era to the other.
• Use either the BC–AD or the BCE–CE notation consistently within the same article. Exception: do not change direct quotations, titles, etc.
• An article's established era style should not be changed without reasons specific to its content; seek consensus on the talk page first (applying Wikipedia:Manual of Style § Retaining existing styles) by opening a discussion under a heading using the word era, and briefly stating why the style should be changed.
• BCE and CE or BC and AD are written in upper case, unspaced, without a full stop (period), and separated from the numeric year by a space (5 BC, not 5BC). It is advisable to use a non-breaking space.
• AD appears before or after a year (AD 106, 106 AD); the other abbreviations appear only after (106 CE, 3700 BCE, 3700 BC).
• In general, omit CE or AD, unless to avoid ambiguity or awkwardness
• Typically, write The Norman Conquest took place in 1066 not 1066 CE nor AD 1066
• But Plotinus lived at the end of the 3rd century AD (not simply at the end of the 3rd century) may avoid confusion unless the era is clear from context.
• One- and two-digit years may look more natural with an era marker (born in 2 AD or born January 15, 22 CE, not born in 2 nor January 15, 22).
• Ranges beginning in BC/BCE should specify the ending era: write 450 to 200 BCE or 450 BC to 200 BC or 450 BCE to 200 CE, but not 450 BCE to 200. (see Ranges)
• Uncalibrated (BCE) radiocarbon dates: Calibrated and uncalibrated dates can diverge widely, and some sources distinguish the two only via BCE or BC (for calibrated dates) versus bce or bc (uncalibrated). When feasible, avoid uncalibrated dates except in direct quotations, and even then ideally give the calibrated date in a footnote or square-bracketed note – [3250 BCE calibrated], or at least indicate the date type – [uncalibrated]. This also applies to other dating systems in which a calibration distinction in drawn.
• BP or YBP: In scientific and academic contexts, BP (Before Present) or YBP (years Before Present) are often used. (Present in this context by convention refers to January 1, 1950.) Write 3000 years BP or 3000 YBP or 3000 years before present but not forms such as 3000 before present and 3000 years before the present. If one of the abbreviated forms is used, link to Before Present on first use: The Jones artifact was dated to 4000  YBP, the Smith artifact to 5000 YBP.
• Other era systems may be appropriate in an article. In such cases, dates should be followed by a conversion to Anno Domini or Common Era, and the first instance linked: Qasr-al-Khalifa was built in 221  AH (836 CE), or in 836 AD (221  AH).
• Astronomical year numbering is similar to the Common Era. There is no need to follow a year expressed with astronomical year numbering with a conversion to Common Era. The first instance of a non-positive year should still be linked: The March equinox passed into Pisces in year −67. (The expressions −67 and 68 BCE refer to the same year.)

#### Julian and Gregorian calendars

A date can be given in any appropriate calendar, as long as it is (at the minimum) given in the Julian calendar or the Gregorian calendar or both, as described below. For example, an article on the early history of Islam may give dates in both Islamic and Julian calendars. Where a calendar other than the Julian or Gregorian is used, the article must make this clear.

• Current events are dated using the Gregorian calendar.
• Dates of events in countries using the Gregorian calendar at that time are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 14 September 1752, and Russia from 14 February 1918 .
• Dates before 15 October 1582 (when the Gregorian calendar was first adopted in some places) are normally given in the Julian calendar.
• Dates after 4 October 1582 in a place where the Julian calendar was observed should be given in the Julian calendar.
• For either the Julian or Gregorian calendars, the beginning of the year should be treated as 1 January even if a different start-of-year date was observed in the place being discussed.
• Dates for Roman history before 45 BC are given in the Roman calendar, which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
• For dates in early Egyptian and Mesopotamian history, Julian or Gregorian equivalents are often uncertain. Follow the consensus of reliable sources, or indicate their divergence.

The dating method used should follow that used by reliable secondary sources (or if reliable sources disagree, that used most commonly, with an explanatory footnote). The guidance above is in line with the usage of reliable sources such as American National Biography, [1] Oxford Dictionary of National Biography, and Encyclopædia Britannica [g]

Where it's not obvious that a given date should be given in Julian alone or in Gregorian alone, consider giving both styles, for example by using {{ OldStyleDate}}. If a date appears without being specified as Old Style or New Style, tagging that date with {{ which calendar?}} will add the page to Category:Articles containing ambiguous dates for further attention.

If an article contains Julian calendar dates after 4 October 1582 (as in the October Revolution), or if a start-of-year date other than 1 January was in force in the place being discussed, or both, a footnote should be provided on the first usage, explaining the calendar usage adopted for the article. The calendar usage should be compatible with this guideline.

#### Ranges

• A simple year–year range is written using an en dash (–, &ndash; or {{ ndash}}), not an em dash, hyphen, or slash; this dash is unspaced (that is, with no space on either side); and the end year is usually given in full:
• 1881–1882;  1881–1886 (not 1881–86);  1881–1992 (not 1881–92)
• Markup: 1881{{ ndash}}1882 or 1881&ndash;1882
• Although non-abbreviated years are generally preferred, two-digit ending years (1881–82, but never 1881–882 or 1881–2) may be used in any of the following cases: (1) two consecutive years; (2) infoboxes and tables where space is limited (using a single format consistently in any given table column); and (3) in certain topic areas if there is a very good reason, such as matching the established convention of reliable sources. [h] For consistency, avoid abbreviated year ranges when they would be used alongside non-abbreviated ranges within an article (or related pages, if in titles). Never use abbreviated years for ranges across centuries (1999–2002, 1999–02) or for years from the first millennium (886–887, 886–87).
• The slash notation (2005/2006) may be used to signify a fiscal year or other special period, if that convention is used in reliable sources.
• Other "simple" ranges use an unspaced en dash as well:
• day–day: 5–7 January 1979;  January 5–7, 1979;  elections were held March 5–8.
• month–month: the 1940 peak period was May–July;  the peak period was May–July 1940;  (but the peak period was May 1940 – July 1940 uses a spaced en dash; see below)
• If at least one item on either side of the en dash contains a space, then a spaced en dash ({{ snd}}) is used. For example:
• between specific dates in different months: They travelled June 3 – August 18, 1952;  They travelled 3 June – 18 August 1952
• between dates in different years:
• Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist ...
• Markup: 12{{ nbsp}}February 1809{{ snd}}19{{ nbsp}}April 1882 or 12&nbsp;February 1809&nbsp;&ndash; 19&nbsp;April 1882
• Abraham Lincoln (February 12, 1809 – April 15, 1865) was the 16th President of ...
• between months in different years: The exception was in force August 1892 – January 1903;  The Ghent Incursion (March 1822 – January 1, 1823) was ended by the New Year's Treaty
• Markup: March 1822{{ snd}}January{{ nbsp}}1, 1823 or March 1822&nbsp;&ndash; January&nbsp;1, 1823
• Where era designations, circa or other modifiers are present: reigned 150 BCE – 50 BCE; reigned 5 BC – 12 AD; reigned c. 1393 – 1414.

• For ranges "to present", constructions such as 1982–present (with unspaced en dash), January 1, 2011 – present (spaced ndash), or January 2011 – present (spaced ndash) may be used, but other constructions may be more appropriate in prose . In tables and infoboxes where space is limited, pres. may be used (1982–pres.). Do not use incomplete-looking constructions such as 1982– and 1982–... .
• For a person still living: Serena Williams (born September 26, 1981) is a ..., not (September 26, 1981 – ) or (born on September 26, 1981).

Do not use * to indicate born; use b. only where space is limited e.g. tables and infoboxes; use either born or b. consistently in any given table column.

• Where birthdate is unknown: John Smith (died May 1, 1622) or John Smith (died 1622)

Do not use † to indicate died; use d. only where space is limited, with consistency within any given table column.

• An overnight period may be expressed using a slash between two contiguous dates: the night raids of 30/31 May 1942 or raids of 31 May / 1 June 1942.

Or use an en dash: (unspaced) raids of 30–31 May 1942;  (spaced) raids of 31 May – 1 June 1942.

• Use an en dash, or a word such as from or between, but not both: from 1881 to 1886 (not from 1881–1886);  between June 1 and July 3 (not between June 1 – July 3)
• The {{ Age}} template can keep ages current in infoboxes and so on:
• {{age|1989|7|23}} returns: 32
• {{age|1989|7|23}}-year-old returns: 32-year-old
• {{age|1989|7|23}} years old returns: 32 years old
• Date mathematics templates are available for other age calculations.

#### Uncertain, incomplete, or approximate dates

• To indicate "around", "approximately", or "about", the use of the spaced, unitalicised form c. 1291 (or the {{ circa}} template) is preferred over circa, ca, ca., around, approximately, or approx.:
• At the birth of Roger Bacon (c. 1214) ...
• John Sayer ( c. 1750 – 2 October 1818) ...
• the Igehalkid dynasty of Elam, c. 1400 BC ...
• Where both endpoints of a range are approximate, c. should appear before each date (the two-argument form of {{ circa}} does this):
• Dionysius Exiguus ( c. 470 – c. 540 ... (not Dionysius Exiguus ( c. 470 – 540) ...)
• Rameses III (reigned c. 1180 – c. 1150 BCE) ... (not Rameses III (reigned c. 1180 – 1150 BCE) ...)
• Where birth/death limits have been inferred from known dates of activity:
• Offa of Mercia (before 734 – 26 July 796) ...
• Robert Menli Lyon (1789 – after 1863) ...
• Ambrose Gwinnett Bierce (June 24, 1842 – after December 26, 1913) ...
• When birth and death dates are unknown, but the person is known to have been active ("flourishing") during certain years, fl., [[Floruit|fl.]], or {{ fl.}} may be used:
• Jacobus Flori ( fl. 1571–1588) ...
The linked forms should not be used on disambiguation pages, and "active" followed by the range is a better alternative for occupations not relating to the composition of works, whether it be musical, grammatical, historical, or any other such work.
• When a date is known to be either of two years (e.g. from a regnal or AH year conversion, or a known age at death):
• Anne Smith (born 1912 or 1913; died 2013) ...
• Other forms of uncertainty should be expressed in words, either in article text or in a footnote: April 14, 1224 (unattested date). Do not use a question mark (1291?), because it fails to communicate the nature of the uncertainty.
• Where c., after, or a similar form appears which applies only to one of the two endpoints of the range, use a spaced en dash ({{snd}}) and ideally a non-breaking space should follow very short modifiers such as c.. Examples: 1896 – after 1954, c. 470 – c. 540. Markup: 1896{{snd}}after 1954, {{c.|470|540}}.
• If the modifier applies to the range as a whole, use an unspaced en dash: fl. 1571–1588; traditionally 1571–1588.

### Times of day

Context determines whether the 12- or 24-hour clock is used. In all cases, colons separate hours, minutes, and (where present) seconds, e.g. 1:38:09 pm or 13:38:09. Use figures (11 a.m. or 12:45 p.m.) rather than words (twelve forty-five p.m.).

• 12-hour clock times end with lower-case a.m. or p.m., or am or pm, preceded by a non-breaking space, e.g. 2:30 p.m. or 2:30 pm (markup: 2:30{{ nbsp}}p.m. or 2:30{{ nbsp}}pm), not 2:30p.m. or 2:30pm. Hours should not have a leading zero (e.g. 2:30 p.m., not 02:30 p.m.). Usually, use noon and midnight rather than 12 pm and 12 am; whether "midnight" refers to the start or the end of a date should be explicitly specified unless clear from the context. Where several times that are all a.m. or all p.m. appear in close proximity, then a.m. or p.m. need be given only once if there is no risk of confusion.
• 24-hour clock times have no a.m., p.m., noon or midnight suffix, and include a colon (15:30 not 1530). Hours under 10 should have a leading zero (08:15). The time 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date, but 24 should not be used for the first hour of the next day (e.g. use 00:10 for ten minutes after midnight, not 24:10).

#### Time zones

Give dates and times appropriate to the time zone where an event took place. For example, the date of the attack on Pearl Harbor should be December 7, 1941 (Hawaii time/​date). Give priority to the place at which the event had its most significant effects; for example, if a hacker in Monaco attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. In some cases, the best solution may be to add the date and time in Coordinated Universal Time (UTC). For example:

8 p.m. Eastern Standard Time on January 15, 2001 (01:00 UTC, January 16)

Alternatively, include just the UTC offset:

21:00  British Summer Time ( UTC+1) on 27 July 2012

Rarely, the time zone in which an event took place has since changed; for example, China until 1949 was divided into five time zones, whereas all of modern China is UTC+8. Similarly, the term "UTC" is not appropriate for dates before this system was adopted in 1960; [2] Universal Time (UT) is the appropriate term for the mean time at the prime meridian (Greenwich) when it is unnecessary to specify the precise definition of the time scale. Be sure to show the UTC or offset appropriate to the clock time in use at the time of the event, not the modern time zone, if they differ.

### Days of the week

• Where space is limited (e.g. tables), days of the week may be abbreviated as Sun, Mon, Tue, Wed, Thu, Fri, Sat.

### Seasons of the year

• Seasons are uncapitalized (a hot summer) except when personified: Jack Frost is a variant of Old Man Winter.
• Avoid the use of seasons to refer to a particular time of year (winter 1995) as such uses are ambiguous: the seasons are six months apart in the northern and southern hemispheres; winter in the northern hemisphere, and summer in the southern hemisphere, span two calendar years; and areas near the equator have only wet and dry seasons. Unambiguous alternatives include early 1995;  the first quarter of 1995;  January to March 1995;  spent the southern summer in Antarctica.
• Referring to a season by name is appropriate when it is part of a formal or conventional name or designation (annual mid-winter festival;  the autumn harvest;  2018 Winter Olympics;  Times Fall Books Supplement;  Details appeared in Quarterly Review, Summer 2015;  The Court's winter term).

• To refer to a decade as a chronological period per se (not with reference to a social era or cultural phenomenon), always use four digits as in the 1980s. Do not use the 1980's, the 1980‑ies, or the 1980s' (unless a possessive is actually meant).
• Prefixes should be hyphenated (the mid‑1980s;  pre‑1960s social attitudes).
• Adjectives should not be hyphenated (the late 1950s, the early 1970s).
• For a social era or cultural phenomenon associated with a particular decade:
• Two digits (with a preceding apostrophe) may be used as an alternative to four digits, but only if this is a well-established phrase seen in reliable sources (the Roaring '20s,  the Gay '90s,  condemning the '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971, and do not write the 90's;  the 90s;  or the 90s').
• A third alternative (where seen in reliable sources) is to spell the decade out, capitalized: changing attitudes of the Sixties.

### Centuries and millennia

The sequence of numbered years in dates runs ... 2 BC, 1 BC, 1 AD, 2 AD ...; there is no " year zero".

• Treat the 1st century AD as years 1–100, the 17th century as 1601–1700, and the second millennium as 1001–2000; similarly, the 1st century BC/BCE was 100–1 BC/BCE, the 17th century BC/BCE was 1700–1601 BC/BCE, and the second millennium 2000–1001 BC/BCE.
• Centuries and millennia are identified using either "Arabic" numerals (the 18th century) or words (the second millennium). When used adjectivally they contain a hyphen (nineteenth-century painting or 19th-century painting). Do not use superscripts (19th century).
• Do not capitalize (the best Nineteenth-century paintings;  during the Nineteenth Century)
• Do not use Roman numerals (XVIII century).
• The 18th century refers to the period (1701–1800), while strictly the 1700s refers either to (1700–1799) or (1700–1709)
• When using forms such as the 1900s, ensure there is no ambiguity as to whether the century or just its first decade is meant.
• See WP:Manual of Style § En dashes for use of hyphens and dashes in obscure situations.

### Long periods of time

• When the term is frequent, combine yr (years) or ya (years ago) with k (thousand): kya, kyr; M (million): Mya, Myr; and b ( short-scale billion): bya, byr. (See Year § Abbreviations yr and ya for more information.)
• In academic contexts, SI annus-based units are often used: ka (kiloannus), Ma (megaannus), and Ga (gigaannus). (See Year § SI prefix multipliers for more information.)
• Show the meaning parenthetically, and consider linking to the appropriate section of the Year article on first occurrence and where the use is a standalone topic of interest. In source quotations, use square brackets: "a measured Libby radiocarbon date of 35.1 Mya [million years ago] required calibration ..."

## Numbers

### Numbers as figures or words

Information on specific situations is scattered elsewhere on this page.

Generally, in article text:

• Integers from zero to nine are spelled out in words.
• Integers greater than nine expressible in one or two words may be expressed either in numerals or in words (16 or sixteen, 84 or eighty-four, 200 or two hundred). When written as words, numbers from 21 to 99 are hyphenated (including when part of a larger number): fifty-six or fifty-six thousand but five hundred or five thousand.
• Other numbers are given in numerals (3.75, 544) or in forms such as 21 million. Markup: 21{{nbsp}}million
• Billion and trillion are understood to represent their short-scale values of 109 (1,000,000,000) and 1012 (1,000,000,000,000), respectively. Keep this in mind when translating articles from non-English or older sources.
• M (unspaced, capitalized) or bn (unspaced), respectively, may be used for "million" or "billion" after a number, when the word has been spelled out at the first occurrence (Her estate of £61 million was split among her husband (£1M), her son (£5M), her butler (£10M), and her three Weimaraners (£15M each).).
• SI prefixes and symbols, such as mega- (M), giga- (G) and tera- (T), should be used only with units of measure as appropriate to the field and not to express large quantities in other contexts. Examples of misuse: In a population of 1.3G people, 300 megadeaths would be expected.
• In the specific case of thousands, there are few if any situations in which e.g. 5 thousand or 250 thousand would be preferable to 5000, 5,000, or 250,000. [i]
• Sometimes, the variety of English used in an article may suggest the use of a numbering system other than the Western thousands-based system. For example, the South Asian numbering system is conventionally used for certain things (especially monetary amounts) in South Asian English. This is discouraged in Wikipedia articles by WP:Manual of Style § Opportunities for commonality.
• When it is done anyway, for contextually important reasons, link the first spelled-out instance of each quantity (e.g. [[crore]], which yields: crore). If no instances are spelled out, provide a note after the first instance, directing the reader to the article about the numbering system.
• Provide a conversion to Western numbers for the first instance of each quantity (the templates {{ lakh}}, {{ crore}}, and {{ lakh crore}} may be used for this purpose), and provide conversions for subsequent instances if they do not overwhelm the content of the article. For example, write three crore (thirty million). When converting a currency amount, use the exchange rate that applied at the time being written about; the {{ INRConvert}} template can be used for this purpose.
• Group digits in Western thousands-based style (e.g., 30,000,000; not 3,00,00,000); see § Delimiting (grouping of digits), below.
• The variety of English does not uniquely determine the method of numbering in an article. Other considerations – such as conventions used in mathematics, science, and engineering – may also apply. The choice and order of formats and conversions is a matter of editorial discretion and consensus at the article.

Notes and exceptions:

• Avoid beginning a sentence with a figure:
• Use: There were many matches; 23 ended in a draw. Or: There were many matches. Twenty-three ended in a draw.
• Not: There were many matches. 23 ended in a draw.
• Use: No elections were held in 1945 and 1950.
• Not: 1945 and 1950 had no elections. (Nor: Nineteen forty-five and 1950 had no elections comparable numbers should be both written in words or both in figures.)
• Opening a sentence with a proper name or technical term that begins with a numeral can usually be avoided by rewording:
• Prefer: Typically, 1-naphthylamine is synthesized via the Feldenshlager–Glockenspiel process. Or: Feldenshlager–Glockenspiel is the process typically used in the synthesis of 1-naphthylamine.
• Avoid: 1-Naphthylamine is typically synthesized via the Feldenshlager–Glockenspiel process.
• In tables and infoboxes, quantities are expressed in figures (Years in office: 5); but numbers within a table's explanatory text and comments follow the general rule.
• Numbers in mathematical formulae are never spelled out (3 < π < 22/7, not three < pi < twenty-two sevenths).
• Sport scores and vote tallies should be given as figures, even if in the zero-to-nine range (a 25–7 victory; and passed with 7 ayes, 2 nays, and 1 abstention).
• Comparable values should be all spelled out or all in figures, even if one of the numbers would normally be written differently: patients' ages were five, seven, and thirty-two or ages were 5, 7, and 32, but not ages were five, seven, and 32.
• Similar guidance applies where "mixed units" are used to represent a single value (as is often done with time durations, and in the imperial and US customary systems): 5 feet 11 inches tall; five feet eleven inches tall; 3 minutes 27 seconds; three minutes twenty-seven seconds.
• Adjacent quantities not comparable should ideally be in different formats: twelve 90-minute volumes or 12 ninety-minute volumes, not 12 90-minute volumes or twelve ninety-minute volumes.
• Avoid awkward juxtapositions: On February 25, 2011, twenty-one more were chosen, not On February 25, 2011, 21 more were chosen.
• Sometimes figures and words carry different meanings; for example, Every locker except one was searched implies there is a single exception (without specifying which), while Every locker except 1 was searched means that locker number 1 was the only locker not searched.
• Proper names, technical terms, and the like are never altered: ,  ,  ,  Seven Samurai,  The Sixth Sense,  ,  ,  The Third Man,  ,  ,  Zero Hour!,
• Figures as figures: Use a figure when the figure itself (its glyph, shape, etc.) is meant: a figure-8 pattern; in the shape of the numeral 6.
• Only figures are used with unit symbols (12 min not twelve min); but figures or words may be used with unit names (12 minutes or twelve minutes), subject to the provisions above.

### Ordinals

• For guidance on choosing between e.g. 15th and fifteenth, see § Numbers as figures or words.
• In "suffix" forms, use two-letter suffixes: 1st, 2nd, 3rd, 4th and so on (2nd Battalion not 2d Battalion). Do not superscript (123rd).
• Do not use ordinals for dates (see MOS:BADDATE).
• In English text, do not use a dot (.) or the ordinal indicator (º). The masculine º or feminine (ª) ordinal indicator is acceptable in names, quotations, etc. from languages that conventionally use it. An Italian example: 313º Gruppo Addestramento Acrobatico not 313º Acrobatic Training Group or the 313º. Use HTML markup for languages that don't have a special character but conventionally use a superscript, like 2es in French.
• Regnal numbers are normally written with ASCII Roman numerals (without suffix, e.g. Elizabeth II not Elizabeth IInd or Elizabeth 2nd).

### Number ranges

As with date ranges (see above), number ranges in general, such as page ranges, should state the full value of both the beginning and end of the range, with an en dash between, e.g. pp. 1902–1911 or entries 342–349. Except in quotations, avoid abbreviated forms such as 1902–11 and 342–9 as they are not understood universally, are sometimes ambiguous, and can cause inconsistent metadata to be created in citations.

### Singular versus plural

• Nouns following simple fractions are singular (took 14 dose;  net change was −12 point;  32 dose).
• Nouns following mixed numbers are plural (112 doses;  another 434 miles).
• Nouns following the lone, unsigned digit 1 are singular, but those following other decimal numbers (i.e. base-10 numbers not involving fractions) are plural (increased 0.7 percentage points;  365.25 days;  paid 5 dollars per work hour, 1 dollar per travel hour, 0 dollars per standby hour;  increased by 1 point but net change +1 points;  net change −1 points;  net change 1.0 points).
• The same rules apply to numbers given in words (one dose;  one and one-half doses;  zero dollars;  net change of negative one points).

### Fractions and ratios

• Spelled-out fractions are hyphenated: seven-eighths.
• Where numerator and denominator can each be expressed in one word, a fraction is usually spelled out (e.g. a two-thirds majority;  moved one-quarter mile); use figures if a fraction appears with a symbol (e.g. 14 mi – markup: {{frac|1|4}}&nbsp;mi, not a quarter of a mi or one-quarter mi). A common exception is a series of values: The distances were 1+14, 23 and 12 mile, respectively.
• Mixed numbers are usually given in figures, unspaced (not Fellini's film 8 12 or 8-12 but Fellini's film 8+12 – markup: {{frac|8|1|2}}). In any case the integer and fractional parts should be consistent (not nine and 12).
• Metric (SI) measurements generally use decimals, not fractions (5.25 mm, not 514 mm).
• Non-metric (imperial and US customary) measurements may use fractions or decimals (514 inches; 5.25 inches); the practice of reliable sources should be followed, and within-article consistency is desirable.
• In science and mathematics articles, mixed numbers are rarely used (use 4/3 the original rather than 11/3 times the original voltage). The use of {{ frac}} is discouraged in favor of one of these styles:
• ${\displaystyle \textstyle {\frac {1}{2}}}$ – markup: < math>\textstyle\frac{1}{2}</math>
• 1/2 – markup: {{ sfrac|1|2}}
• 1/2 – markup: 1/2
• Do not use precomposed fraction characters such as ½ (deprecated markup: &frac12; or &#189;). Exception: In special situations such as articles on chess matches, a precomposed ½ may be used if that is the only fraction appearing in the article.
• Ordinal suffixes such as -th should not be used with fractions expressed in figures (not each US state has 1/50th of the Senate's votes; 1/8th mile, but one-fiftieth of the Senate's votes; 1/8 mile; one-eighth mile).
• Dimensionless ratios (i.e. those without accompanying units) are given by placing a colon between integers, or placing to between numbers-as-words: favored by a 3:1 ratio or a three-to-one ratio, not a 3/1 ratio or a 3–1 ratio.
• Use a colon (spaced) when one or more decimal points is present (a 3.5 : 1 ratio – markup: a 3.5&nbsp;:&nbsp;1 ratio).
• Do not use the colon form where units are involved (dissolve using a 3 ml : 1 g ratio)‍—‌instead see ratios section of table at § Unit names and symbols, below.

### Decimals

• A period/full point (.) – never a comma – is used as the decimal point (6.57, not 6,57).
• Numbers between −1 and +1 require a leading zero (0.02, not .02); exceptions are sporting performance averages (.430 batting average) and commonly used terms such as .22 caliber.
• Indicate repeating digits with an overbar e.g. 14.31{{overline|28}} gives 14.3128. (Consider explaining this notation on first use.) Do not write e.g. 14.31(28) because it resembles notation for uncertainty.

### Grouping of digits

• Digits should be grouped and separated either by commas or by narrow gaps (never a period/full point).
• Grouping with commas
Left of the decimal point, five or more digits are grouped into threes separated by commas (e.g. 12,200; 255,200 km; 8,274,527th; 186,400).
Numbers with exactly four digits left of the decimal point may optionally be grouped (either 1,250 or 1250), with consistency within any given article.
When commas are used left of the decimal point, digits right of the decimal point are not grouped (i.e. should be given as an unbroken string).
Markup: {{ formatnum:}} produces this formatting.
• Grouping with narrow gaps
Digits are grouped both sides of the decimal point (e.g. 6543210.123456; 520.01234 °C; 101325/760).
Digits are generally grouped into threes. Right of the decimal point, usual practice is to have a final group of four in preference to leaving an "orphaned" digit at the end (99.1234567, but 99.1234567 would also be acceptable). In mathematics-oriented articles long strings may be grouped into fives (e.g. 3.14159265358979323846...).
This style is especially recommended for articles related to science, technology, engineering or mathematics.
Markup: Templates {{ val}} or {{ gaps}} may be used to produce this formatting. Note that use of any space character as a separator in numbers, including non-breaking space, is problematic for screen readers. (See § Non-breaking spaces.) Screen readers read out each group of digits as separate numbers (e.g. 30{{ thin space}}000 is read as "thirty zero zero zero".)
• Delimiting style should be consistent throughout a given article.
• Either use commas or narrow gaps, but not both in the same article.
• Either group the thousands in a four-digit number or do not, but not mixed use in the same article.
• However, grouping by threes and fives may coexist.
• An exception is made for four-digit page numbers or four-digit calendar years. These should never be grouped (not sailed in 1,492, but dynasty collapsed around 10,400 BC or by 13727 AD, Vega will be the northern pole star).

### Percentages

• In the body of non-scientific/non-technical articles, percent (American English) or per cent (British English) are commonly used: 10 percent; ten percent; 4.5 per cent. Ranges are written ten to twelve per cent or ten to twelve percent, not ten–twelve per cent.
• In the body of scientific/​technical articles, and in tables and infoboxes of any article, the symbol % (unspaced) is more common: 3%, not 3 % or three %. Ranges: 10–12%, not 10%–12% or 10 to 12%.
• When expressing the difference between two percentages, do not confuse a percentage change with a change in percentage points.

### Scientific and engineering notation

• Scientific notation always has a single nonzero digit to the left of the point: not 60.22×1022, but 6.022×1023.
• Engineering notation is similar, but with the exponent adjusted to a multiple of three: 602.2×1021.
• Avoid mixing scientific and engineering notations (A 2.23×102 m2 region covered by 234.0×106 grains of sand).
• In a table column (or other presentation) in which all values can be expressed with a single power of 10, consider giving e.g. ×107 once in the column header, and omitting it in the individual entries. (Markup: {{e|7}})
• In both notations, the number of digits indicates the precision. For example, 5×103 means rounded to the nearest thousand; 5.0×103 to the nearest hundred; 5.00×103 to the nearest ten; and 5.000×103 to the nearest unit.

Markup: {{ val}} and {{ e}} may be used to format exponential notation.

### Uncertainty and rounding

• Where explicit uncertainty information (such as a margin of error) is available and appropriate for inclusion, it may be written in various ways:
• (1.534 ± 0.035) × 1023 m
• 12.34 m2 ± 5% (not used with scientific notation)
• 15.34 +0.43
−0.23
× 1023 m
• 1.604(48) × 10−4 J (equivalent to (1.604 ± 0.048) × 10−4 J) [j]
• Polls estimated Jones's share of the vote would be 55 percent, give or take about 3 percent
• Markup: {{ +-}}, {{ su}}, and {{ val}} may be used to format uncertainties.
• Where explicit uncertainty is unavailable (or is unimportant for the article's purposes) round to an appropriate number of significant digits; the precision presented should usually be conservative. Precise values (often given in sources for formal or matter-of-record reasons) should be used only where stable and appropriate to the context, or significant in themselves for some special reason.
• The speed of light is defined to be 299,792,458 m/s
• but Particle velocities eventually reached almost two-thirds the 300-million-metre-per-second speed of light.
• checks worth $250 (equivalent to$1,800 in 2016) (not $1,845.38 in 2016) • The city's 1920 population was 10,000 (not population was 9,996 – an official figure unlikely to be accurate at full precision) • but The town was ineligible because its official census figure (9,996) fell short of the statutory minimum of ten thousand (unusual case in which the full-precision official figure is truly informative) • The accident killed 337 passengers and crew, and 21 people on the ground (likely that accurate and precise figures were determined) • At least 800 persons died in the ensuing mudslides (unlikely that any precise number can be accurate, even if an official figure is issued) • or Officials listed 835 deaths, but the Red Cross said dozens more may have gone unreported (in reporting conflicting information, give detail sufficient to make the contrast intelligible) • The jury's award was$8.5 million (not $8,462,247.63). The appeals court reduced this to$3,000,001 (one dollar in actual damages, the remainder in punitive damages).
• The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not 41 and 47.4 percent), unless different precisions are actually intended.
• It may sometimes be appropriate to note the lack of uncertainty information, especially where such information is normally provided and necessary for full interpretation of the figures supplied.
• A local newspaper poll predicted 52 percent of the vote would go to Smith, but did not include information on the uncertainty of this estimate
• The {{ undue precision}} template may be added to figures appearing to be overprecise.
• Avoid using "approximately", "about", and similar terms with figures that have merely been approximated or rounded in a normal and expected way, unless the reader might otherwise be misled.
• The tallest player was 6 feet 3 inches (not ... about 6 feet 3 inches – heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle)
• but The witness said the assailant was about 5 feet 8 inches tall ("about" because here the precise value is unknown, with substantial uncertainty)
• The reader may be assumed to interpret large round numbers (100,000 troops) as approximations. Writing a quantity in words (one hundred thousand troops) can further emphasize its approximate nature.
• See § Unit conversions below for precision issues when converting units.

### Non–base 10 notations

• In computer-related articles, use the prefix 0x for hexadecimal and 0b for binary, [k] unless there is a strong reason to use some other notation. [l] Explain these prefixes in the article's introduction or on first use.
• In all other articles, use <sub> to create subscripts: 1379, 2013. Markup: 137<sub>9</sub>, 201<sub>3</sub>
• For bases above 10, use symbols conventional for that base (as seen in reliable sources) e.g. for base 16 use 0–9 and A–F.
• For octal, the prefix 0 is unclear (0201) and other prefixes may be unfamiliar; avoid using a prefix unless it is needed for computer code samples, in which case explain the prefix on first use. In prose, use the subscript 8 (2018).

### Mathematical formulae

There are multiple ways to display mathematical formulae, covered in detail at Wikipedia:Manual of Style/Mathematics § Typesetting of mathematical formulae. One uses special MediaWiki <math>...</math> markup using LaTeX syntax, which is capable of complex formulae; the other relies on conventionalized HTML formatting of simple formulae.

The <math> markup is displayed as a PNG image by default. Logged-in users can optionally have it rendered in MathML, or in HTML (via MathJax); detailed instructions are at Help:Displaying a formula.

## Units of measurement

### Unit choice and order

Quantities are typically expressed using an appropriate "primary unit", displayed first, followed, when appropriate, by a conversion in parentheses e.g. 200 kilometres (120 mi). For details on when and how to provide a conversion, see the section § Unit conversions. The choice of primary units depends on the circumstances, and should respect the principle of " strong national ties", where applicable:

• In non-scientific articles with strong ties to the United States, the primary units are US customary (pounds, miles, feet, inches, etc.)
• In non-scientific articles with strong ties to the United Kingdom, the primary units for most quantities are metric or other internationally used units, [m] except that:
• UK engineering-related articles, including those on bridges and tunnels, generally use the system of units in which the subject project was drawn up (but road distances are given in imperial units, with a metric conversion – see next bullet);
• the primary units for distance/​length, speed and fuel consumption are miles, miles per hour, and miles per imperial gallon (except for short distances or lengths, where miles are too large for practical use);
• the primary units for personal height and weight are feet​/inches and stones/​pounds;
• imperial pints are used for quantities of draught beer/​cider and bottled milk;
• In all other articles, the primary units chosen will be SI units, non-SI units officially accepted for use with the SI, or such other units as are conventional in reliable-source discussions of the article topic (such as revolutions per minute (rpm) for rotational speed, hands for heights of horses, etc.).

Special considerations:

• Quantities set via definition (as opposed to measured quantities) should be given first in the units used in the definition, even if this makes the structure of presentation inconsistent: During metrification, the speed limit was changed from 30 mph (48 km/h) to 50 km/h (31 mph).
• Or use about to emphasize which is the statutory, exact value: ...from 30 mph (about 48 km/h) to 50 km/h (about 31 mph).
• Nominal quantities (e.g. 2 × 4 lumber) require consideration of whether the article is concerned with the item's actual dimensions or merely with its function. In some cases, the nominal quantity may suffice; in others it may be necessary to give the nominal size (often in non-SI units), the actual size in non-SI units, and the actual size in SI units.
• Whenever a conversion is given, the converted quantity's value should match the precision of the source (see § Unit conversions).
• Where the article's primary units differ from the units given in the source, the {{ convert}} template's |order=flip flag can be used; this causes the original unit to be shown as secondary in the article, and the converted unit to be shown as primary: {{convert|200|mi|km|order=flip}}The two cities are 320 kilometres (200 mi) apart.

### Unit conversions

Where English-speaking countries use different units for the same quantity, provide a conversion in parentheses: the Mississippi River is 2,320 miles (3,734 km) long; the Murray River is 2,508 kilometres (1,558 mi) long. But in science-related articles, supplying such conversion is not required unless there is some special reason to do so.

• Where an imperial unit is not part of the US customary system, or vice versa – and in particular, where those systems give a single term different definitions – a double conversion may be appropriate: Rosie weighed 80 kilograms (180 lb; 12 st 8 lb) (markup: {{convert|80|kg|lb stlb}}); The car had a fuel economy of 5 L/100 km (47 mpg‑US; 56 mpg‑imp) (markup: {{convert|5|L/100km|mpgus mpgimp|abbr=on}}).
• Generally, conversions to and from metric units and US or imperial units should be provided, except:
• When inserting a conversion would make a common or linked expression awkward (The four-minute mile).
• In some topic areas (for example maritime subjects where nautical miles are the primary units, or American football where yards are primary) it can be excessive to provide a conversion for every quantity. In such cases consider noting that the article will use a particular unit – possibly giving the conversion factor to other, familiar units in a parenthetical note or a footnote – and link the first occurrence of each unit but not give a conversion every time it occurs. Applying this principle may require editorial discretion; for example, in scientific articles the expected level of reader sophistication should be taken into account.
• Converted quantity values should use a level of precision similar to that of the source quantity value, so the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). Small numbers, especially if approximate, may need to be converted to a range where rounding would cause a significant distortion, so about one mile (1–2 km), not about one mile (2 km). Be careful especially when your source has already converted from the units you're now converting back to. This may be evidenced by multiples of common conversion factors in the data, such as 160 km (from 100 miles). See false precision.
• {{ convert}} (and other conversion templates) can be used to convert and format many common units.
• In a direct quotation, always retain the source units. Any conversions can be supplied either in the quote itself (in square brackets, following the original measurement) or in a footnote. See footnoting and citing sources.
• {{ Units attention}} may be added to articles needing general attention regarding choice of units and unit conversions.

### Unit names and symbols

Definitions:
• Examples of unit names: foot, metre, kilometre, (US: meter, kilometer).
• Examples of unit symbols: ft, m, km.
• Unit names and symbols should follow the practice of reliable sources.
• In prose, unit names should be given in full if used only a few times, but symbols may be used when a unit (especially one with a long name) is used repeatedly, after spelling out the first use (e.g. Up to 15 kilograms of filler is used for a batch of 250 kg).
• Exception: Certain units are generally represented by their symbols (e.g. °C rather than degrees Celsius) even on first use, though their unit names may be used for emphasis or clarity (conversion of degrees Celsius to degrees Fahrenheit).
• Exception: Consider using inches (but not in.) in place of in where the latter might be misread as a preposition‍—‌but not where the value is followed by a parenthesized conversion e.g. bolts 5 in (12.7 cm) long, or is part of such a conversion (bolts 12.7 cm (5 in) long).
• Where space is limited, such as in tables, infoboxes, parenthetical notes, and mathematical formulas, unit symbols are preferred.
• Units unfamiliar to general readers should be presented as a name–symbol pair on first use, linking the unit name (Energies rose from 2.3 megaelectronvolts (MeV) to 6 MeV).
• Ranges use unspaced en dash ({{ ndash}}) if only one unit symbol is used at the end (e.g. 5.9–6.3 kg), and spaced en dash ({{ snd}}) if two symbols are used (e.g. 3 μm – 1 mm); ranges in prose may be specified using either unit symbol or unit names, and units may be stated either after both numerical values or after the last (all acceptable: from 5.9 to 6.3 kilograms; from 5.9 kilograms to 6.3 kilograms; from 5.9 to 6.3 kg; from 5.9 kg to 6.3 kg).
• Length–width, length–width–height and similar dimensions may be separated by the multiplication sign (× or &times;) or the word by.
• The × symbol is preceded by a space (preferably non-breaking), and followed by a space (which may also be non-breaking in short constructions), and each number should be followed by a unit name or symbol:
• 1 m × 3 m × 6 m, not 1 × 3 × 6 m, (1 × 3 × 6) m, nor 1 × 3 × 6 m3
• a metal plate 1 ft × 3 ft × 0.25 in
• a railroad easement 10 ft × 2.5 mi
• With by, the unit need be given only once if it is the same for all dimensions: 1 by 3 by 6 metres or 1 by 3 by 6 m
• The unspaced letter x may be used in common terms such as .
General guidelines on use of units
Aspect
Guideline Acceptable Unacceptable
Unit names and symbols
Except as listed in the § Specific units table below, unit symbols are uncapi­tal­ized unless they are derived from a proper name, in which case the first letter (of the base unit symbol, not of any prefix) is capitalized. [n] 8 kg
100 kPa
8 Kg
100 kpa
Unit symbols are undotted. 38 cm of rope 38 cm. of rope
Unit names are given in lower case except: where any word would be capital­ized, or where otherwise specified in the SI brochure [4] or this Manual of Style.
• A gallon is 4 quarts.
• 4 pascals
• A Gallon is 4 Quarts.
• 4 Pascals
• He walked several miles.
• Miles of trenches were dug.
The spelling of certain unit names (some of which are listed in § Specific units, below) varies with the variety of English followed by the article.
Write unit names and symbols in upright ( roman) type, except where emphasizing in context. 10 m
29 kilograms
10 m
29 kilograms
Thus each two-liter jug contained only two quarts.
Do not use precomposed unit symbol characters. ㎓, ㎦, ㎍, ㎖, ㎉
Numeric values
Do not spell out numbers before unit symbols ... 12 min twelve min
... but words or figures may be used with unit names.
• twelve minutes
• 12 minutes
Use a non-breaking space ({{ nbsp}} or &nbsp;) between a number and a unit symbol, or use {{ nowrap}} ... 29 kg (markup: 29&nbsp;kg or {{nowrap|29 kg}}) 29kg
... though with certain symbols no space is used (see "Specific units" table below) ... 23° 47′ 22″ 23 ° 47  22
... and a normal space is used between a number and a unit name. 29 kilograms
(markup: 29 kilograms)
To form a value and a unit name into a compound adjective use a hyphen or hyphens ...
• a five-day holiday
• a five-cubic-foot box
• a 10-centimeter blade
... but a non-breaking space (never hyphen) separates a value and unit symbol.
• a blade 10 cm long
Plurals
SI unit names are pluralized by adding the appropriate -s or -es suffix ... 1 ohm; 10 ohms
... except for these irregular forms. 1 henry; 10 henries
1 hertz; 10 hertz
1 lux; 10 lux
1 siemens; 10 siemens
10 henrys
10 hertzes
10 luxes
10 siemenses
Some non-SI units have irregular plurals. 1 foot; 10 feet 10 foots
1 stratum; 10 strata (unusual) 10 stratums
Unit symbols (in any system) are identical in singular and plural.
• grew from 1 in to 2 in
• grew from 1 inch to 2 inches
• grew from one to two inches
grew from 1 in to 2 ins
Powers
Format exponents using <sup>, not special characters. km2
(markup: km<sup>2</sup>)
km²
(km&#178;)
Or use squared or cubed (after the unit being modified). ten metres per second squared ten metres per squared second
For areas or volumes only, square or cubic may be used (before the unit being modified). ten metres per square second
tons per square mile
sq or cu may be used with US customary or imperial units, but not with SI units. 15 sq mi
3 cu ft
15 sq km
3 cu m
Products
Indicate a product of unit names with either a hyphen or a space.
• foot-pound
• foot pound
• footpound
• foot⋅pound
Indicate a product of unit symbols with & sdot; or & nbsp;.
• ms = millisecond
• m⋅s or m s = metre-second
Exception: In some topic areas, such as power engineer­ing, certain products take neither space nor &sdot;. Follow the practice of reliable sources in the article's topic area.
To pluralize a product of unit names, pluralize only the final unit. (Unit symbols are never pluralized.) ten foot-pounds ten feet-pounds
Ratios, rates, densities
Indicate a ratio of unit names with per. meter per second meter/second
Indicate a ratio of unit symbols with a forward slash (/), followed by either a single symbol or a parenthesized product of symbols – do not use multiple slashes. Or use −1, −2, etc.
• metre per second
• m/s
• m⋅s−1
• mps
• kg/(m⋅s)
• kg⋅m−1⋅s−1
• kg/m⋅s
• kg/m/s
To pluralize a ratio of unit names, pluralize only the numerator unit. (Unit symbols are never pluralized.)
• ten newton-metres per second
• 10 N⋅m/s
Some of the special forms used in the imperial and US customary systems are shown here ...
• mph = miles per hour
• mpg = miles per gallon
• psi = pounds per square inch
... but only the slash or negative exponent notations are used with SI (and other metric) units.
• g/m2
• g⋅m−2
gsm
• km/h
• km⋅h−1
kph
Prefixes
Prefixes should not be separated by a space or hyphen. kilopascal
• kilo pascal
• kilo-pascal
Prefixes are added without contraction, except as shown here: kilohm
megohm
hectare
kiloohm
megaohm
hectoare
The deci-, deca-, and hecto- prefixes should generally be avoided; exceptions include decibel, hectolitre, hectare, and hectopascal.
• 100 metres
• 0.1 km
1 hectometre
Do not use M for 103, MM for 106, or B for 109 (except as noted elsewhere on this page for M and B, e.g. for monetary values) 3 km
8 MW
125 GeV
3 Mm
8 MMW
125 BeV
Mixed units
Mixed units are traditionally used with the imperial and US customary systems ...
• a wall 1 ft 1 in thick
• a wall 1 foot 1 inch thick
• a man 6 feet 2 inches tall
• a 6-foot 2-inch man
• a 6 ft 2 in man
• 1 ft , 1 in (no comma)
• 1 foot , 1 inch
• a man 6 foot 2 tall
• a 6-foot 2 man
•
• 1 US fl pt 8 oz
• 1 US fl pt 8 US fl oz
... and in expressing time durations ...
• 1:30′07″
• 1:30′
• 1 hr 30 min 7 sec
• 1 h 30 m 7 s
... but are not normally used in metric units.
• 1.33 m
• 133 cm
1 m 33 cm

Note to table:

1. ^ Use this format only where it is clear from context whether it means hours and minutes (H:MM) or minutes and seconds (M:SS).
2. ^ This format is used in astronomy (see the IAU Style Manual [6] for details).

### Specific units

• The following table lists only units that need special attention.
• The SI Brochure [4] should be consulted for guidance on use of other SI and non-SI units.
Guidelines on specific units
Group
Name Symbol Comment
Length, speed
• inch
• foot
• in
• ft
Do not use &prime; (), &Prime; (), apostrophe ('), or quote (").
foot per second ft/s (not fps)
hand h or hh Equal to 4 inches; used in measurement of horses. A dot may be followed by additional inches e.g. 16.2 hh indicates 16 hands 2 inches.
• kn (not , , or )
• KIAS or kn
• KCAS
• KEAS
• KTAS
• kn (not KGS)
Used in aviation contexts for aircraft and wind speeds, and also used in some nautical and general meteorological contexts. When applied to aircraft speeds, kn means KIAS unless stated otherwise; if kn is used for calibrated airspeed, equivalent airspeed, true airspeed, or groundspeed, explicitly state and link to, upon first use, the type of speed being referred to (for instance, , or, if severely short of space, kn EAS); for airspeeds other than indicated airspeed, the use of the specific abbreviation for the type of airspeed being referred to (such as KEAS) is preferred. When referring to indicated airspeed, either kn or KIAS is permissible. Groundspeeds and wind speeds must use the abbreviation kn only.
• metre
• meter (US)
m
micron μm (not μ) Markup: &mu;m  Link to micrometre (for which micron is a synonym) on first use.
astronomical unit au
(not A.U., ua)
The preferred option is au. Articles that already use AU may switch to au or continue with AU; seek consensus on the talk page.
• mile
• miles per hour
• nautical mile
• mi
• mph
• nmi or NM (not or M)
In nautical and aeronautical contexts where there is risk of confusion with nautical miles, consider writing out references to statute miles as e.g. 5 statute miles rather than simply 5 miles.
Volume, flow
• cubic centimetre
• cubic centimeter (US)
cm3 Markup: cm<sup>3</sup>
cc Non-SI abbreviation used for certain engine displacements. Link to Cubic centimetre on first use.
• imperial fluid ounce
• imperial pint
• imperial quart
• imperial gallon
• US fluid ounce
• US fluid pint
• US fluid quart
• US gallon
• imp fl oz
• imp pt
• imp qt
• imp gal
• US fl oz
• US fl pt
• US fl qt
• US gal
US or imperial (or imp) must be specified; fluid or fl must be specified for fluid ounces and US units, except with gallon. (Without fluid, ounce is ambiguous – versus avoirdupois ounce or troy ounce – and US pint or US quart are ambiguous – versus US dry pint or US dry quart.)
cubic foot cu ft (not cf) Write five million cubic feet, 5,000,000 cu ft, or 5×106 cu ft, not 5 MCF.
cubic foot per second cu ft/s (not cfs)
• litre
• liter (US)
L (not l or ) The symbol l (lowercase "el") in isolation (i.e. outside forms as ml) is easily mistaken for the digit 1 or the capital letter I ("eye") and should not be used.
• millilitre
• milliliter (US)
ml or mL Derivative units of the litre may use l (lowercase "el") as guided by WP:ENGVAR.
Mass, weight, force, density, pressure
• gram
• kilogram
• g
• kg
Not gramme, kilogramme
• long ton
• short ton
Spell out in full.
t (not mt, MT, or )
pound per square inch psi
troy ounce oz t t or troy must be specified. Articles about precious metals, black powder, and gemstones should always specify whether ounces and pounds are avoirdupois or troy.
troy pound lb t
carat carat Used to express masses of gemstones and pearls.
Purity
carat or karat k or Kt (not or ) A measure of purity for gold alloys. (Do not confuse with the unit of mass with the same spelling.)
Time
• second
• minute
• hour
• s
• min
• h
Do not use &prime; (), &Prime; (), apostrophe (') or quote (") for minutes or seconds. See also the hours–minutes–seconds formats for time durations described in the Unit names and symbols table.
year a Use a only with an SI prefix multiplier (a rock formation 540 Ma old, not Life expectancy rose to 60 a).
y or yr See § Long periods of time for all affected units.
Information, data
bit bit (not b or B) See also § Quantities of bytes and bits, below. Do not confuse bit/second or byte/second with baud (Bd).
byte B or byte (not b or )
bit per second bit/s (not bps, b/s)
byte per second B/s or byte/s (not Bps, bps, b/s)
Angle
arcminute Markup: &prime;  ( prime ′ not apostrophe/​single quote '). No space (47′, not 47 ).
arcsecond Markup: &Prime;  ( double prime ″ not double-quote "). No space (22″, not 22 ).
degree ° Markup: &deg; (degree ° not masculine ordinal º or ring ̊ ). No space (23°, not 23 °).
Temperature
degree Fahrenheit °F (not F) Markup: &deg;. Use a non-breaking space: 12{{ nbsp}}&deg;C, not 12&deg;C nor 12&deg;{{ nbsp}}C (12 °C, not 12°C nor 12° C).
degrees Rankine °R (not R)
degree Celsius (not degree centigrade) °C (not C)
kelvin (not degree kelvin) K (not °K) Use a non-breaking space: 12{{nbsp}}K
U+004B K LATIN CAPITAL LETTER K and not U+212A K KELVIN SIGN
Energy
• calorie
• small calorie
• gram calorie
cal In certain subject areas, calorie is convention­ally used alone; articles following this practice should specify on first use whether the use refers to the small calorie or to the kilocalorie (large calorie). Providing conversions to SI units (usually calories to joules or kilocalories to kilojoules) may also be useful. A kilocalorie (kcal) is 1000 calories. A calorie (small calorie) is the amount of energy required to heat 1 gram of water by 1 °C. A kilocalorie is also a kilogram calorie.
• kilocalorie
• large calorie
• kilogram calorie
• (not Calorie – can be ambiguous)
kcal

#### Quantities of bytes and bits

In quantities of bits and bytes, the prefixes kilo- (symbol k or K), mega- (M), giga- (G), tera- (T), etc., are ambiguous in general usage. The meaning may be based on a decimal system (like the standard SI prefixes), meaning 103, 106, 109, 1012, etc., or it may be based on a binary system, meaning 210, 220, 230, 240, etc. The binary meanings are more commonly used in relation to solid-state memory (such as RAM), while the decimal meanings are more common for data transmission rates, disk storage and in theoretical calculations in modern academic textbooks.

Prefixes for multiples of
bits (bit) or bytes (B)
Decimal
Value SI
1000 k kilo
10002 M mega
10003 G giga
10004 T tera
10005 P peta
10006 E exa
10007 Z zetta
10008 Y yotta
Binary
Value IEC Memory
1024 Ki kibi K kilo
10242 Mi mebi M mega
10243 Gi gibi G giga
10244 Ti tebi T tera
10245 Pi pebi
10246 Ei exbi
10247 Zi zebi
10248 Yi yobi

Follow these recommendations when using these prefixes in Wikipedia articles:

• Following the SI standard, a lower-case k should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital K should be used instead to indicate the binary prefix for 1024 according to JEDEC. If, under the exceptions detailed further below, the article otherwise uses IEC prefixes for binary units, use Ki instead.
• Do not assume that the binary or decimal meaning of prefixes will be obvious to everyone. Explicitly specify the meaning of k and K as well as the primary meaning of M, G, T, etc. in an article ({{ BDprefix}} is a convenient helper). Consistency within each article is desirable, but the need for consistency may be balanced with other considerations.
• The definition most relevant to the article should be chosen as primary for that article, e.g. specify a binary definition in an article on RAM, decimal definition in an article on hard drives, bit rates, and a binary definition for Windows file sizes, despite files usually being stored on hard drives.
• Where consistency is not possible, specify wherever there is a deviation from the primary definition.
• Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:
• A 64 MB (64 × 10242-byte) video card and a 100 GB (100 × 10003-byte) hard drive
• A 64 MB (64 × 220-byte) video card and a 100 GB (100 × 109-byte) hard drive
• A 64 MB (67,108,864-byte) video card and a 100 GB (100,000,000,000-byte) hard drive
• Avoid combinations with inconsistent form such as A 64 MB (67,108,864-byte) video card and a 100 GB (100 × 10003-byte) hard drive. Footnotes, such as those seen in Power Macintosh 5500, may be used for disambiguation.
• Unless explicitly stated otherwise, one byte is eight bits (see Byte § History).

The IEC prefixes kibi- (symbol Ki), mebi- (Mi), gibi- (Gi), etc., are generally not to be used except: [o]

• when the majority of cited sources on the article topic use IEC prefixes;
• in a direct quote using the IEC prefixes;
• when explicitly discussing the IEC prefixes; or
• in articles in which both types of prefix are used with neither clearly primary, or in which converting all quantities to one or the other type would be misleading or lose necessary precision, or declaring the actual meaning of a unit on each use would be impractical.

## Currencies and monetary values

Choice of currency

• In country-specific articles, such as Economy of Australia, use the currency of the subject country.
• In non-country-specific articles such as Wealth, use US dollars (US$123 on first use, generally$123 thereafter), euros (€123), or pounds sterling (£123).

Currency names

• Do not capitalize the names or denominations of currencies, currency subdivisions, coins and banknotes: not a Five-Dollar bill, four Quarters, and one Penny total six Dollars one Cent but a five-dollar bill, four quarters, and one penny total six dollars one cent. Exception: where otherwise required, as at the start of a sentence or in such forms as Australian dollar.
• To pluralize euro use the standard English plurals (ten euros and fifty cents), not the invariant plurals used for European Union legislation and banknotes (ten euro and fifty cent). For the adjectival form, use a hyphenated singular (a two-euro pen and a ten-cent coin).
• Link the first occurrence of lesser-known currencies ().

Currency symbols

• In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. A$52), with subsequent references using just the appropriate symbol (e.g.$88), unless this would be unclear. Exceptions:
• In an article referring to multiple currencies represented by the same symbol (e.g. the dollars of the US, Canada, Australia, New Zealand, and other countries – ) use the full signifier (e.g. US$or A$, but not e.g. $US123 or$123 (US)) each time, except (possibly) where a particular context makes this both unnecessary and undesirable.
• In articles entirely on EU-, UK- and/or US-related topics, all occurrences may be shortened (€26, £22 or $34), unless this would be unclear. • For the British pound sterling (GBP), use the £ symbol, with one horizontal bar, not the double-barred (which is used for Italian lira). For non-British currencies that use pounds or a pound symbol (e.g. the Egyptian pound, E£) use the symbol conventionally employed for that currency. • If there is no common English abbreviation or symbol, follow the ISO 4217 standard. See also List of circulating currencies. • Link the first occurrence of lesser-known currency symbols () Formatting • A period (full stop, .) – never a comma – is used as the decimal point ($6.57, not $6,57). • For the grouping of digits (e.g. £1,234,567) see § Grouping of digits, above. • Do not place a currency symbol after the accompanying numeric figures (e.g. 123$, 123£, 123€) unless that is the normal convention for that symbol when writing in English: smaller British coins include 1p, 2p, and 5p denominations.
• Currency abbreviations preceding a numeric value are unspaced if they consist of a nonalphabetic symbol alone (£123 or €123), or end with a nonalphabetic symbol ( R$123); but spaced (using {{ nbsp}}) if completely alphabetic ( R 123 or JD 123). • Ranges should be expressed giving the currency signifier just once:$250–300, not $250–$300.
• million and billion should be spelled out on first use, and (optionally) abbreviated M or bn (both unspaced) thereafter: She received £70 million and her son £10M; the school's share was $250–300 million, and the charity's$400–450M.
• In general, a currency symbol should be accompanied by a numeric amount e.g. not He converted his US$to A$ but He converted his US dollars to Australian dollars or He exchanged the US$100 note for Australian dollars. • Exceptions may occur in tables and infoboxes where space is limited e.g. Currencies accepted: US$, SFr, GB£, . It may be appropriate to wikilink such uses, or add an explanatory note.

Conversions

• Conversions of less-familiar currencies may be provided in terms of more familiar currencies – such as the US dollar, euro or pound sterling – using an appropriate rate (which is often not the current exchange rate). Conversions should be in parentheses after the original currency, along with the convert-to year; e.g. the grant in 2001 was 10,000,000 Swedish kronor ($1.4M, €970,000, or £850,000 as of 2009) • For obsolete currencies, provide an equivalent (formatted as a conversion) if possible, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings), or a US-dollar equivalent where there is no modern equivalent. • In some cases, it may be appropriate to provide a conversion accounting for inflation or deflation over time. See {{ Inflation}} and {{ Inflation-fn}}. • When converting among currencies or inflating/deflating, it is rarely appropriate to give the converted amount to more than three significant figures; typically, only two significant figures are justified: the grant in 2001 was 10,000,000 Swedish kronor ($1.4M, €970,000, or £850,000), not (\$1,390,570, €971,673 or £848,646)

## Common mathematical symbols

• The Insert menu below the editing window gives a more complete list of math symbols, and allows symbols to be inserted without the HTML encoding (e.g. &divide;) shown here.
• Spaces are placed to left and right when a symbol is used (the sum 4 + 5), but no space is used when (the value +5). Exception: spaces are usually omitted in inline fractions formed with /: 3/4 not 3 / 4.
• The {{ mvar}} (for single-letter variables) and {{ math}} (for more complicated expressions) templates are available to display mathematical formulas in a manner distinct from surrounding text.
• The {{ nbsp}} and {{ nowrap}} templates may be used to prevent awkward linebreaks.
Common mathematical symbols
Symbol name Example Markup Comments
Plus /
positive
x + y {{math|''x'' + ''y''}}
+y {{math|+''y''}}
Minus /
negative
xy {{math|''x'' &minus; ''y''}} Do not use hyphens (-) or dashes ({{ ndash}} or {{ mdash}}).
y {{math|&minus;''y''}}
Plus-minus /
minus-plus
41.5 ± 0.3 41.5 &plusmn; 0.3
−(±a) = ∓a {{math|1=&minus;(&plusmn;''a'') = &#8723;''a''}}
Multiplication,
dot
xy {{math|''x'' &sdot; ''y''}}
Multiplication,
cross
x × y {{math|''x'' &times; ''y''}} Do not use the letter x to indicate multiplication. However, an unspaced x may be used as a substitute for "by" in common terms such as 4x4.
Division, obelus x ÷ y {{math|''x'' &divide; ''y''}}
Equal / equals x = y {{math|1=''x'' = ''y''}} or
{{math|''x'' {{=}} ''y''}}
Note the use of 1= or {{=}} to make the template parameters work correctly
Not equal xy {{math|''x'' &ne; ''y''}}
Approx. equal π ≈ 3.14 {{math|''&pi;'' &asymp; 3.14}}
Less than x < y {{math|''x'' &lt; ''y''}}
Less or equal xy {{math|''x'' &le; ''y''}}
Greater than x > y {{math|''x'' &gt; ''y''}}
Greater or equal xy {{math|''x'' &ge; ''y''}}

## Geographical coordinates

For draft guidance on, and examples of, coordinates for linear features, see Wikipedia:WikiProject Geographical coordinates/Linear.
Quick guide:

To add to the top of an article, use {{ Coord}}, thus:

{{Coord|57|18|22|N|4|27|32|W|display=title}}

These coordinates are in degrees, minutes, and seconds of arc.

"title" means that the coordinates will be displayed next to the article's title at the top of the page (in desktop view only; title coordinates do not display in mobile view) and before any other text or images. It also records the coordinates as the primary location of the page's subject in Wikipedia's geosearch API.

To add to the top of an article, use either

{{Coord|44.1124|N|87.9130|W|display=title}}

(which does not require minutes or seconds but does require the user to specify north/ south and east/west) or

{{Coord|44.1124|-87.9130|display=title}}

(in which the north and east are presumed by positive values while the south and west are negative ones) These coordinates are in decimal degrees.

• Degrees, minutes and seconds, when used, must each be separated by a pipe ("|").
• Map datum must be WGS84 (except for off-Earth bodies).
• Avoid excessive precision (0.0001° is <11 m, 1″ is <31 m).
• Maintain consistency of decimal places or minutes/seconds between latitude and longitude.
• Latitude (N/S) must appear before longitude (E/W).

Optional coordinate parameters follow the longitude and are separated by an underscore ("_"):

• dim: dim:N (viewing diameter in metres)
• region: region:R ( ISO 3166-1 alpha-2 or ISO 3166-2 code)
• type: type:T (landmark or city(30,000), for example)

Other optional parameters are separated by a pipe ("|"):

• display
|display=inline (the default) to display in the body of the article only,
|display=title to display at the top of the article only (in desktop view only; title coordinates do not display in mobile view), or
|display=inline,title to display in both places.
• name
name=X to label the place on maps (default is PAGENAME)

Thus: {{Coord|44.1172|-87.9135|dim:30_region:US-WI_type:event

|display=inline,title|name=accident site}}

Use |display=title (or |display=inline,title) once per article, for the subject of the article, where appropriate.

Geographical coordinates on Earth should be entered using a template to standardise the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, a robot performs the functions automatically.

First, obtain the coordinates. Avoid excessive precision.

The {{ Coord}} template offers users a choice of display format through user styles, emits a Geo microformat, and is recognised (in the title position) by the "nearby" feature of Wikipedia's mobile apps and by external service providers such as Google Maps and Google Earth, and Yahoo. Infoboxes automatically emit {{ Coord}}.

The following formats are available.

• For degrees only (including decimal values): {{coord|dd|N/S|dd|E/W}}
• For degrees/minutes: {{coord|dd|mm|N/S|dd|mm|E/W}}
• For degrees/minutes/seconds: {{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• dd, mm, ss are the degrees, minutes and seconds, respectively;
• N/S is either N for northern or S for southern latitudes;
• E/W is either E for eastern or W for western longitudes;
• negative values may be used in lieu of S and W to denote Southern and Western Hemispheres

For example:

For the city of Oslo, located at 59° 54′ 50″ N, 10° 45′ 8″ E:

{{coord|59|54|50|N|10|45|08|E}} – which becomes

For a country, like Botswana, with no source on an exact geographic center, less precision is appropriate due to uncertainty:

{{coord|22|S|24|E}} – which becomes

Higher levels of precision are obtained by using seconds:

{{coord|33|56|24|N|118|24|00|W}} – which becomes

Coordinates can be entered as decimal values:

{{coord|33.94|S|118.40|W}} – which becomes

Increasing or decreasing the number of decimal places controls the precision. Trailing zeros may be added as needed to give both values the same appearance.

London Heathrow Airport, Amsterdam, Jan Mayen and Mount Baker are examples of articles that contain geographical coordinates.

Generally, the larger the object being mapped, the less precise the coordinates should be. For example, if just giving the location of a city, precision greater than degrees (°), minutes (′), seconds (″) is not needed, which sufficient to locate, for example, the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10 meters or even one meter in some cases (1″ ~15 m to 30 m, 0.0001° ~5.6 m to 10 m).

The final field, following the E/W, is available for attributes such as type:, region:, or scale: (the codes are documented at Template:Coord/doc § Coordinate parameters).

When adding coordinates, please remove the {{ coord missing}} tag from the article, if present (often at the bottom).

For more information, see the geographical coordinates WikiProject.

Templates other than {{ coord}} should use the following variable names for coordinates: lat_d, lat_m, lat_s, lat_NS, long_d, long_m, long_s, long_EW.

## Notes

1. ^ See Arbitration Committee statements of principles in cases on style-related edit warring in June 2005, November 2005, and February 2006; and Wikipedia:General sanctions/Units in the United Kingdom.
2. ^ a b c For use in tables, infoboxes, references, etc. Only certain citation styles use abbreviated date formats. By default, Wikipedia does not abbreviate dates. Use a consistent citation style within any one article.
3. ^ All-numeric yyyy-mm-dd dates might be assumed to follow the ISO 8601 standard, which mandates the Gregorian calendar. Also, technically all years must have (only) four digits, but Wikipedia is unlikely to ever need to format a date beyond the year 9999.
4. ^ The routine linking of dates is deprecated. This change was made August 24, 2008, on the basis of this archived discussion. It was ratified in two December 2008 RfCs: Wikipedia:Manual of Style/Dates and numbers/Three proposals for change to MOSNUM and Wikipedia:Manual of Style/Dates and numbers/Date Linking RFC.
5. ^ For consensus discussion on abbreviated date formats like "Sep 2", see Wikipedia talk:Manual of Style/Archive 151 § RFC: Month abbreviations
6. ^ These formats cannot, in general, be distinguished on sight, because there are usages in which 03-04-2007 represents March 4, and other usages in which it represents April 3. In contrast, there is no common usage in which 2007-04-03 represents anything other than April 3.
7. ^ The calendar practices of Oxford Dictionary of National Biography and Encyclopædia Britannica can be inferred by looking up the birth and death dates of famous, well-documented individuals.
8. ^ A change from a preference for two digits, to a preference for four digits, on the right side of year–year ranges was implemented in July 2016 per this RFC.
9. ^ And positively don't write 5 hundred or 25 hundred thousand.
10. ^ The number in parentheses in a construction like 1.604(48) × 10−4 J is the numerical value of the standard uncertainty referred to the corresponding last digits of the quoted result. [3]
11. ^ The 0x, but not 0b, is borrowed from the C programming language.
12. ^ One such situation is with Unicode codepoints, which use U+; U+FDD0, not 0xFDD0.
13. ^ If there is disagreement about the primary units used in a UK-related article, discuss the matter on the article talk-page or at Wikipedia talk:Manual of Style/Dates and numbers ( WT:MOSNUM). If consensus cannot be reached, refer to historically stable versions of the article and retain the units used in these as the primary units. Also note the style guides of British publications (e.g. The Times, under "Metric").
14. ^ These definitions are consistent with all units of measure mentioned in the SI Brochure [4] and with all units of measure catalogued in EU directive 80/181/EEC. [5]
15. ^ Wikipedia follows common practice regarding bytes and other data traditionally quantified using binary prefixes (e.g. mega- and kilo-, meaning 220 and 210 respectively) and their unit symbols (e.g. MB and KB) for RAM and decimal prefixes for most other uses. Despite the IEC's 1998 international standard creating several new binary prefixes (e.g. mebi-, kibi-, etc.) to distinguish the meaning of the decimal SI prefixes (e.g. mega- and kilo-, meaning 106 and 103 respectively) from the binary ones, and the subsequent incorporation of these IEC prefixes into the ISO/IEC 80000, consensus on Wikipedia in computing-related contexts favours the retention of the more familiar but ambiguous units KB, MB, GB, TB, PB, EB, etc. over use of unambiguous IEC binary prefixes. For detailed discussion, see WT:Manual of Style (dates and numbers)/Archive/Complete rewrite of Units of Measurements (June 2008).

## References

1. ^ Garraty, John A.; Carnes, Mark C., eds. (1999). "Editorial note". American National Biography. Oxford University Press. pp. xxi–xxii.
2. ^ Coordinated Universal Time (UTC) (PDF). Bureau International des Poids et Mesures. June 2, 2009. p. 3. CCTF/09-32. Retrieved August 20, 2015. This coordination began on January 1, 1960, and the resulting time scale began to be called informally 'Coordinated Universal Time.'
3. ^ "Fundamental Physical Constants: Standard Uncertainty and Relative Standard Uncertainty". The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 25, 2015. Retrieved December 12, 2017.
4. ^ a b c "Chapter 4: Non-SI units that are accepted for use with the SI". SI Brochure: The International System of Units (SI) (PDF) (9th ed.). Bureau International des Poids et Mesures. 2019. Retrieved 2020-09-24. Table 8, p 145, gives additional guidance on non-SI units.
5. ^ "Council Directive of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement". Eur-Lex.Europa.eu. European Union. 2017 [1979]. 80/181/EEC (Document 01980L0181-20090527). Retrieved December 12, 2017.
6. ^ Wilkins, G. A. (1989). "5.14 Time and angle". IAU Style Manual (PDF). International Astronomical Union. p. S23. Retrieved 12 December 2017.