Kilometre

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Categories: Units of length | Orders of magnitude (length)

"km" redirects here. For other uses, see KM.

**1 kilometre** =
SI units
1000 m	1×10⁶ mm
US customary / Imperial units
0.621 mi	3,280 ft

A kilometre (American spelling: kilometer, symbol km) is a unit of length in the metric system, equal to one thousand metres, the current SI base unit of length. It can be written in scientific notations as 1×10³ m (engineering notation) or 1 E+3 m (exponential notation) — both meaning 1,000 × 1 m.

A corresponding unit of area is the square kilometre and a corresponding unit of volume is the cubic kilometre.

Although, in English, metric units of measurement are usually pronounced with the stress on the first syllable, as in /ˈkɪl.əˌmiː.tə(r)/, pronunciation of the word "kilometre" with the stress on the second syllable /kɪˈlɒm.ə.tə(r)/ is in common usage (see List of words of disputed pronunciation). The latter pronunciation follows the stress pattern used for the names of measuring instruments, such as barometer, thermometer, tachometer and speedometer. This stress pattern is not commonly used for other metric measurements such as millimetre or centimetre.

Slang terms for kilometre include ""click" (sometimes spelled "klick" or "klik") and "kay" (or "k"). These non-standard terms can also refer to kilometres per hour, which itself is abbreviated as km/h, km h^-1, km·h^-1 or, informally, kph.

"Kilometrage" may be used in the same way as "mileage".

1 Equivalence to other units of length
2 International usage
3 Unicode symbols
4 References
5 See also

Equivalence to other units of length

1 kilometre is equal to:

1,000 metres (1 metre is equal to 0.001 kilometres)
about 0.621 statute miles (1 statute mile is equal to 1.609344 kilometres)
- the formula "multiply by 5 and divide by 8" gives a conversion of 0.625, accurate to 0.6%, which is a useful approximation
about 1,094 international yards (1 international yard is equal to 0.0009144 kilometres)
about 3,281 feet (1 foot is equal to 0.0003048 kilometres)

International usage

The United Kingdom and the United States of America are the only two developed countries that have not changed their road signs from miles to kilometres.

Although the UK has officially adopted the metric system, there is no intention to replace the mile on road signs in the near future, owing to the British public's attachment to traditional imperial units of distance, i.e., miles, yards and inches, the enormous cost that would be involved in changing road signs^[1], and the fact that car speedometers in the UK mainly measure miles per hour^[2]. As of 11 September 2007, the EU has allowed Britain to continue using the imperial systems. EU commissioner Günter Verheugen said: "There is not now and never will be any requirement to drop imperial measurements."^[3]

In the US, the National Highway System Designation Act of 1995 prohibits the use of federal-aid highway funds to convert existing signs or purchase new signs with metric units.^[4] However, the Manual on Uniform Traffic Control Devices since 2000 published in both metric and American Customary Units. (See also Metrication in the United States.)