Centimetre

File:CarpentersRule.png
A carpenters' ruler with centimetre divisions

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${\displaystyle ^{-2}}$.[1] Hence a centimetre can be written as 10×10${\displaystyle ^{-3}}$ m (engineering notation) or 1 E-2 m (scientific E notation) — meaning 10 × 1 mm or 1 m / 100 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.

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 centimeters)
• about 0.393700787401575 inches (1 inch is equal to 2.54 centimetres exactly) [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 centimeter 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${\displaystyle ^{-12}}$ Farad [4]
• in Canadian maps, centimetres are used to make conversions from map scale to real world scale (kilometers)

Unicode symbols

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

• centimetre (cm) - 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.