# Centimetre

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<math>^{-2}</math>.^{[1]} Hence a centimetre can be written as 10×10<math>^{-3}</math> 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 10^{3} - 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<math>^{-12}</math> 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.

## See also

- 1 E-2 m
- SI
- SI prefix
- Metric system
- Orders of magnitude (length)
- Conversion of units, for comparison with other units of length

## References

- ↑ http://www.bipm.org/en/si/si_brochure/chapter3/prefixes.html
- ↑ http://scienceworld.wolfram.com/physics/Inch.html
- ↑ http://www.weathershack.com/education/rain-measurement.html
- ↑ http://scienceworld.wolfram.com/physics/Capacitance.html
- ↑ [1] CJK Compatibility excerpt from The Unicode Standard, Version 4.1.

## External links

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