Centimetre
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Centimetre
Centimetre
A carpenter's ruler with centimetre divisions
General information
Unit systemmetric
Unit oflength
Symbolcm
Conversions
SI units10 mm
imperial & US system~0.3937 in

A centimetre (international spelling as used by the International Bureau of Weights and Measures; symbol cm) or centimeter (American spelling) 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] 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.

## Equivalence to other units of length

 1 centimetre = 10 millimetres = 0.01 metres = 0.393700787401574803149606299212598425196850 inches (There are exactly 2.54 centimetres in one inch.)

One millilitre is defined as one cubic centimetre, under the SI system of units.

## Other uses

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 [2]
• in the CGS system, the centimetre is used to measure capacitance, where 1 cm of capacitance = farads[3]
• 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.

## Unicode symbols

For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:[4]

• centimetre (cm) - code 339D
• square centimetre (cm^2) - code 33A0
• cubic centimetre (cm^3) - code 33A4

They are mostly used only with East Asian fixed-width CJK fonts, because they are equal in size to one Chinese character.

## References

1. ^ "Decimal multiples and submultiples of SI units". Bureau International des Poids et Mesures. 2014. Retrieved 2015.
2. ^ Rain Measurement, Rain Gauge, Wireless Rain Gauge, Rain Gage, Rain Gauge Data
3. ^ Capacitance - from Eric Weisstein's World of Physics
4. ^ CJK Compatibility excerpt from The Unicode Standard, Version 10.0.