"km" redirects here. For other uses, see KM (disambiguation).
Unit system metric
Unit of length
Symbol km
Unit conversions
1 km in ...... is equal to ...
   SI units    1000 m
   imperial/US units    0.62137 mi
3280.8 ft
   nautical units    0.53996 nmi

The kilometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: km; /ˈkɪləmtər/ or /kɪˈlɒmɪtər/) or kilometer (American spelling) is a unit of length in the metric system, equal to one thousand metres (kilo- being the SI prefix for 1000). It is now the measurement unit used officially for expressing distances between geographical places on land in most of the world; notable exceptions are the United States and the road network of the United Kingdom where the statute mile is the official unit used.

k (pronounced /k/) is occasionally used in some English-speaking countries as an alternative for the word kilometre in colloquial writing and speech.[1][2][3] A slang term for the kilometre in the US military is klick.[4]


There are two common pronunciations for the word.[5]

The former follows a pattern in English whereby metric units are pronounced with the stress on the first syllable, and the pronunciation of the actual base unit does not change irrespective of the prefix. It is generally preferred by the British Broadcasting Corporation (BBC) and the Australian Broadcasting Corporation (ABC).

Many scientists and other users, particularly in countries where the metric system is not widely used, use the pronunciation with stress on the second syllable.[6][7] The latter pronunciation follows the stress pattern used for the names of measuring instruments (such as micrometer, barometer, thermometer, tachometer and speedometer). The problem with this reasoning, however, is that the word meter in those usages refers to a measuring device, not a unit of length. The contrast is even more obvious in countries using the British rather than American spelling of the word metre.

When Australia introduced the metric system in 1975, the first pronunciation was declared official by the government's Metric Conversion Board. However, the Australian prime minister at the time, Gough Whitlam, insisted that the second pronunciation was the correct one because of the Greek origins of the two parts of the word.[8]

Equivalence to other units of length

1 kilometre 1000 metres
3281 feet
1094 yards
0.621 miles
0.540 nautical miles
6.68×10−9 astronomical units[9]
1.06×10−13 light-years[10]
3.24×10−14 parsecs


By the 8 May 1790 decree, the Constituent assembly ordered the French Academy of Sciences to develop a new measurement system. In August 1793, the French National Convention decreed the metre as the sole length measurement system in the French Republic. The first name of the kilometre was "Millaire". Although the metre was formally defined in 1799, the myriametre (10000 metres) was preferred to the "kilometre" for everyday use. The term "myriamètre" appeared a number of times in the text of Develey's book Physique d'Emile: ou, Principes de la science de la nature,[11] (published in 1802), while the term kilometre only appeared in an appendix. French maps published in 1835 had scales showing myriametres and "lieues de Poste" (Postal leagues of about 4288 metres).[12]

The Dutch, on the other hand, adopted the kilometre in 1817 but gave it the local name of the mijl.[13] It was only in 1867 that the term "kilometer" became the only official unit of measure in the Netherlands to represent 1000 metres.[14]

Two German textbooks dated 1842[15][16] and 1848[17] respectively give a snapshot of the use of the kilometre across Europe - the kilometre was in use in the Netherlands and in Italy and the myriametre was in use in France.

In 1935, the International Committee for Weights and Measures (CIPM) officially abolished the prefix "myria-" and with it the "myriametre", leaving the kilometre as the recognised unit of length for measurements of that magnitude.[18]

International usage

Chinese expressway distances road sign in eastern Beijing. Although the primary text is in Chinese, the distances use internationally recognised characters.

United Kingdom

In the United Kingdom, road signs show distances in miles[19][20] and location marker posts that are used for reference purposes by road engineers and emergency services show distance references in unspecified units which are kilometre-based.[21] The advent of the mobile phone has been instrumental in the British Department for Transport authorising the use of driver location signs to convey the distance reference information of location marker posts to road users should they need to contact the emergency services.

United States

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.[22] The Executive Director of the US Federal Highway Administration, Jeffrey Paniati, wrote in a 2008 memo: "Section 205(c)(2) of the National Highway System (NHS) Designation Act of 1995 prohibited us from requiring any State DOT [Department of Transport] to use the metric system during project development activities. Although the State DOT's had the option of using metric measurements or dual units (metrics/inch-pounds), all of them abandoned metric measurements and reverted to sole use of inch-pound values."[23] The Manual on Uniform Traffic Control Devices since 2000 is published in both metric and American Customary Units. (See also Metrication in the United States.)

Kilometre records

Some sporting disciplines feature 1000 m (one-kilometre) races in major events (such as the Olympic Games), but in other disciplines, even though world records are catalogued, the one kilometre event remains a minority event. The world records for various sporting disciplines are:

Discipline Name Time (min:s) Location Year Comments
Running (M) Noah Ngeny 2:11.96[24] Rieti, Italy 5 Sep 1999 Not an Olympic event
Running (F) Svetlana Masterkova 2:28.98[25] Brussels 23 Aug 1996 Not an Olympic event
Speed Skating (M) Shani Davis 1:06.42[26] Salt Lake City 7 Mar 2009
Speed Skating (F) Cindy Klassen 1:13.11[26] Calgary 25 Mar 2006
Cycling (M) Arnaud Tourant 58.875[27] La Paz, Bolivia 10 Oct 2001 No official 1000 m woman's record

See also

Notes and references

  1. Walshe, Cathy (18 August 2008). "Triathlon: Hewitt bubbling after top 10 finish". The New Zealand Herald. Retrieved 27 October 2008. The race was four laps, and I was just counting down the k's to the end
  2. Kuschke, Jazz (21 August 2007). "The great north (off) road". Getaway Magazine via Retrieved 27 October 2008. yet less than 10 kays down the road
  3. "Traveling the Roads to Darwin". Enjoy Darwin. Retrieved 27 October 2008. Camooweal just over the Queensland border a further 250 k's along the road
  4. Rod Powers. "How Far is a "Klick" in the Military?". Archived from the original on 13 April 2010. Retrieved 13 April 2010.
  5. Jones, Daniel (2003) [1917], Peter Roach, James Hartmann and Jane Setter, eds., English Pronouncing Dictionary, Cambridge: Cambridge University Press, ISBN 3-12-539683-2
  6. White, Roland (23 March 2008). "Correct pronunciation on the radio". The Times. London. Retrieved 7 May 2010.
  7. "Kilometer - Definition and More from the Free Merriam-Webster Dictionary". Retrieved 2014-08-05.
  8. "damage lessons". Retrieved 2014-08-05.
  9. One astronomical unit is currently accepted to be equal to 149597870691±30 m.
  10. A light-year is equal to 9.4607304725808×1012 km the distance light travels through vacuum in one year (365.25 days).
  11. Develey, Emmanuel (1802). Physique d'Emile: ou, Principes de la science de la nature. 1. Paris.
  12. Map of the department of Hautes Pyrénées (Map). France Pittoresque (in French). Laguillermie et Rambos. 1835. Retrieved 21 September 2012.
  13. Jacob de Gelder (1824). Allereerste Gronden der Cijferkunst [Introduction to Numeracy] (in Dutch). 's-Gravenhage and Amsterdam: de Gebroeders van Cleef. pp. 155–156. Retrieved 2 March 2011.
  14. "[News from] Nederland" (PDF). De Locomotief. Nieuws, handels en Advertentie-blad. 12 August 1869. p. 2.
  15. "Amtliche Maßeinheiten in Europa 1842" [Official units of measure in Europe 1842] (in German). Retrieved 26 March 2011Text version of Malaisé's book
  16. Ferdinand Malaisé (1842). Theoretisch-practischer Unterricht im Rechnen [Theoretical and practical instruction in arithmetic] (in German). München. pp. 307–322. Retrieved 26 March 2011.
  17. Mozhnik, Franz (1848). Lehrbuch des gesammten Rechnens für die vierte Classe der Hauptschulen in den k.k. Staaten. [Arithmetic textbook for the fourth class in the [Austrian] Imperial and [Hungarian] Royal states] (in German). Vienna: Im Verlage der k.k. Schulbücher Verschleiß-Administration. Das Wegmaß. Retrieved 19 July 2013.
  18. McGreevy, Thomas (1997). Cunningham, Peter, ed. The Basis of Measurement - Volume 2 - Metrication and Current Practice. Picton. ISBN 0-948251-84-0.
  19. "Statutory Instrument 2002 No. 3113 - The Traffic Signs Regulations and General Directions". 16 December 2002. Retrieved 12 January 2010.
  20. The Council of the European Communities (27 May 2009). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". Retrieved 12 January 2010.
  21. Hansard. "21 October 2009 : Column 1446W". Retrieved 4 November 2009.
  22. "50th Anniversary of the Interstate Highway System - Frequently Asked Questions". US Department of Transport. Retrieved 12 October 2007.
  23. Update on Metric Use Requirements for FHWA Documents US Department of Transportation, Federal Highway Administration, 25 November 2008.
  24. "Men's World Records". Track and Field. Retrieved 9 November 2011.
  25. "Women's World Records". Track and Field. Retrieved 9 November 2011.
  26. 1 2 "Speed Skating: Complete history list of World Records recognized by ISU" (PDF). International Skating Union. 1 July 2009. Retrieved 9 November 2011.
  27. "Track Records". Union Cycliste Internationale. Retrieved 9 November 2011.
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