Centimetre

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 . 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

{|
|-
|rowspan=4 valign=top|1 centimetre
|= 10 millimetres
|-
|= 0.01 metres
|-
|= 0.39370078740157480314960629921259842519685 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 
 in the CGS system, the centimetre is used to measure capacitance, where 1 cm of capacitance =  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.

Unicode symbols
For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:
 centimetre (㎝) – code 339D
 square centimetre (㎠) – code 33A0
 cubic centimetre (㎤) – code 33A4

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

See also
1 E-2 m
Conversion of units, for comparison with other units of length
Reciprocal centimetre
Orders of magnitude (length)

References

Category:Units of length
-02
Category:Centimetre–gram–second system of units
Category:SI units
Category:100 (number)