This page was last edited on 23 March 2018, at 08:40.

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 1/100.[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.

A carpenter's rule with centimetre divisions
Unit information
Unit system metric
Unit of length
Symbol cm 
Unit conversions
1 cm in ... ... is equal to ...
   SI units    10 mm
   imperial & US system    ~0.3937 in

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 1 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 = 1.113×10−12 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 (㎝) – 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


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