Definitions

# Centimetre

[sen-tuh-mee-ter]

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 current SI base unit of length. Centi is the SI prefix for a factor of 10$^\left\{-2\right\}$. Hence a centimetre can be written as 10×10$^\left\{-3\right\}$ m (engineering notation) or (scientific E notation) — meaning or respectively. The centimetre is the base unit of length in the now deprecated centimetre-gram-second 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.

The centimeter is the distance light travels through a vacuum in $frac\left\{1\right\}\left\{29 979 245 800\right\}$ second.

## Equivalence to other units of length

1 centimetre is equal to:

• 0.01 metres, which can be represented by 1.00 E-2 m (1 metre is equal to 100 centimetres)
• about 0.393700787401575 inches (1 inch is equal to 2.54 centimetres exactly)

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
• in the CGS system, the centimetre is used to measure capacitance, where 1 cm of capacitance = 1.113×10$^\left\{-12\right\}$ Farad
• in Canadian maps, centimetres are used to make conversions from map scale to real world scale (kilometres)

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