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 ^{− 2}.^[1] Hence a centimetre can be written as 10×10 ^{− 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.

The centimetre is the distance light travels through a vacuum in second.

[edit] Equivalence to other units of length

1 centimetre is equal to:

• 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 approximately equal to 2.54 centimetres) ^[2]

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

[edit] 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 Canadian maps, centimetres are used to make conversions from map scale to real world scale (kilometres)

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

[edit] 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

[edit] References

• CJK Compatibility excerpt from The Unicode Standard, Version 4.4 and co-exterior users.

[edit] External links

• Screen-o-meter