centimetre
A carpenter's ruler with centimetre divisions
General information
Unit systemSI
Unit oflength
Symbolcm
Conversions
1 cm in ...... is equal to ...
millimetres   10 mm
imperial & US system   ~0.3937 in
Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter.

A centimetre (international spelling) or centimeter (American spelling) (SI symbol cm) is a unit of length in the International System of Units (SI), 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.

## 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 = 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 – 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.