# Centimetre

1 centimetre =
SI units
10×10−3 m 10 mm
US customary / Imperial units
32.81×10−3 ft 0.39370 in

A centimetre (American spelling: centimeter, symbol cm) is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of 10−2.[1] Hence a centimetre can be written as 1×10−2 m, 10×10−3 m (engineering notation) or 1E−2 m (scientific E notation) — meaning 10 mm or 1 m/100 respectively. The centimetre is 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 adult person (between 3/8 in and 7/16 inch on an English inch ruler).

## Equivalence to other units of length

A carpenters' ruler with centimetre divisions

1 centimetre is equal to:

• 10 millimetres
• 0.01 metre, which can be represented by 1.00 E-2 m (1 metre is equal to 100 centimetres)
• about 0.393700787401575 inch (1 inch is equal to 2.54 centimetres) [2]

1 cubic centimetre is equal to 1 millilitre, under the current SI system of units.

## Uses of centimetre

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 [3]
• in the CGS system, the centimetre is used to measure capacitance, where 1 cm of capacitance = 1.113×10$^{-12}$ Farad [4]
• in maps, centimetres are used to make conversions from map scale to real world scale (kilometres)
• to represent second moment of areas (cm^4)

## Unicode symbols

For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:[5]

• 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.