A centimetre (international spelling) or centimeter (American spelling) (SI symbol cm) is a unit
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 prefix
es 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
is defined as one cubic centimetre, under the SI
system of units.
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 = farad
* 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
For the purposes of compatibility with Chinese
) characters, Unicode
has symbols for:CJK Compatibility excerpt
from The Unicode Standard, Version 10.0.
* 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.
*1 E-2 m
*Conversion of units, for comparison with other units of length
*Orders of magnitude (length)
Category:Units of length
Category:Centimetre–gram–second system of units