|1 cm in ...||... is equal to ...|
|SI units||10 mm|
|imperial & US system||~0.3937 in|
A centimetre (international spelling) or centimeter (American spelling) (SI symbol cm) is a unit of length in the metric system, equal to one hundredth of a metre, centi being the SI prefix for a factor of 1/100.  The centimetre was the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units.
Though for many physical quantities, SI prefixes for factors of 103—like milli- and kilo-—are often preferred by technicians, the centimetre remains a practical unit of length for many everyday measurements. A centimetre is approximately the width of the fingernail of an average adult person.
1 centimetre = 10 millimetres = 0.01 metres = 0.393700787401574803149606299212598425196850 inches (There are exactly 2.54 centimetres in one inch.)
In addition to its use in the measurement of length, the centimetre is used:
- sometimes, to report the level of rainfall as measured by a rain gauge 
- in the CGS system, the centimetre is used to measure capacitance, where 1 cm of capacitance = 1.113×10−12 farads 
- in maps, centimetres are used to make conversions from map scale to real world scale (kilometres)
- to represent second moment of areas (cm4)
- as the inverse of the Kayser, a CGS unit, and thus a non-SI metric unit of wavenumber: 1 kayser = 1 wave per centimetre; or, more generally, (wavenumber in kaysers) = 1/( wavelength in centimetres). The SI unit of wavenumber is the inverse metre, m−1.
- centimetre – U+339D ㎝ SQUARE CM
- square centimetre – U+33A0 ㎠ SQUARE CM SQUARED
- cubic centimetre – U+33A4 ㎤ SQUARE CM CUBED
They are mostly used only with East Asian fixed-width CJK fonts, because they are equal in size to one Chinese character.
- 1 E-2 m
- Conversion of units, for comparison with other units of length
- Reciprocal centimetre
- Orders of magnitude (length)
- "Decimal multiples and submultiples of SI units". Bureau International des Poids et Mesures. 2014. Retrieved 5 July 2015.
- "Rain Measurement". www.weathershack.com.
- Weisstein, Eric W. "Capacitance -- from Eric Weisstein's World of Physics". scienceworld.wolfram.com.
- CJK Compatibility excerpt from The Unicode Standard, Version 10.0.