The kilometre is a unit
Units of measurement
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...

 of length
In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...

 in the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...

, equal to one thousand metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

s and is therefore exactly equal to the distance travelled by light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

 in free space in of a second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

. 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 United Kingdom where the statute mile is the official unit used.

k (kay) is commonly used as an alternative for the word kilometre in everyday writing and speech. A slang
Slang is the use of informal words and expressions that are not considered standard in the speaker's language or dialect but are considered more acceptable when used socially. Slang is often to be found in areas of the lexicon that refer to things considered taboo...

 term for the kilometre in the U.S. military is klick.


There are two common pronunciations for the word: and
The former pronunciation follows the general pattern in English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

 whereby SI units of measurement are pronounced with the stress on the first syllable, and the pronunciation of the actual base unit does not change irresepective 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 (SI) is not widely used, use the pronunciation with stress on the second syllable. 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 English 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
Gough Whitlam
Edward Gough Whitlam, AC, QC , known as Gough Whitlam , served as the 21st Prime Minister of Australia. Whitlam led the Australian Labor Party to power at the 1972 election and retained government at the 1974 election, before being dismissed by Governor-General Sir John Kerr at the climax of the...

, insisted that the second pronunciation was the correct one because of the Greek origins of the two parts of the word.

Equivalence to other units of length

Units are given to three significant figures:
Comparison to other units of length
One (1) kilometre ≡ (1,000) metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

(100,000) centimetre
A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of . Hence a centimetre can be written as or — meaning or respectively...

One (1) kilometre ≈ parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

(0.540) nautical mile
Nautical mile
The nautical mile is a unit of length that is about one minute of arc of latitude along any meridian, but is approximately one minute of arc of longitude only at the equator...

(0.621) statute miles
(1,094) yard
A yard is a unit of length in several different systems including English units, Imperial units and United States customary units. It is equal to 3 feet or 36 inches...

(3,281) feet
1.61 kilometres ≈ One (1) statute mile
A mile is a unit of length, most commonly 5,280 feet . The mile of 5,280 feet is sometimes called the statute mile or land mile to distinguish it from the nautical mile...

Niagara Falls (1039 m)

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The distance between the American extremity of the Niagara Falls
Niagara Falls
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...

 and the Canadian extremity is 1039 m, or fractionally over a kilometre. Although the length of the rim of the Canadian extremity (Horseshoe Falls
Horseshoe Falls
The Horseshoe Falls, also known as the Canadian Falls, is part of Niagara Falls, on the Niagara River. Approximately 90% of the Niagara River, after diversions for hydropower generation, flows over Horseshoe Falls. The remaining 10% flows over the American Falls...

 is quoted as being 790 m and the rim of the American extremity American Falls
American Falls
The American Falls is one of three waterfalls that together are known as Niagara Falls on the Niagara River along the Canada-U.S. border. Unlike the much larger Horseshoe Falls, of which two-thirds of the falls is located in Ontario, Canada and one-third in New York State, United States, the...

 as being 320 m which add up to more than 1110 m, the rim of the Horseshoe falls is far from straight, so the direct distance between the end-points is 304 m.

43.08557°N 79.06885°W NE extremity of American Falls (Prospect Point)

43.07901°N 79.07798°W SW extremity of the Horseshoe Falls

The Mall, London (987 m)

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The Mall, which leads up to Buckingham Palace
Buckingham Palace
Buckingham Palace, in London, is the principal residence and office of the British monarch. Located in the City of Westminster, the palace is a setting for state occasions and royal hospitality...

, is one of London’s
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 main tourist attractions. Immediately in front of the palace is the Victoria Memorial, erected in memory of Queen Victoria (foreground of the picture to the right). At the opposite end is the Admiralty Arch
Admiralty Arch
Admiralty Arch is a large office building in London which incorporates an archway providing road and pedestrian access between The Mall, which extends to the South-West, and Trafalgar Square to the North-East. It was designed by Sir Aston Webb, constructed by John Mowlem & Co and completed in 1912...

 which links The Mall to Trafalgar Square
Trafalgar Square
Trafalgar Square is a public space and tourist attraction in central London, England, United Kingdom. At its centre is Nelson's Column, which is guarded by four lion statues at its base. There are a number of statues and sculptures in the square, with one plinth displaying changing pieces of...

. The distance from the entrance to the Admiralty Arch to the centre of the Victoria Memorial is 987 m.

51.50185°N 0.14064°W Centre of the Victoria Memorial

51.50671°N 0.12876°W Entrance to the Admiralty Arch

Kowloon – Hong Kong Crossing (1007 m)

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Hong Kong Harbour boasts one of the busiest waterways in the world. Until 1970 the only way to cross the harbour was the Star Ferry
Star Ferry
The Star Ferry, or The "Star" Ferry Company, is a passenger ferry service operator in Hong Kong. Its principal routes carry passengers across Victoria Harbour, between Hong Kong Island and Kowloon...

 which had terminals on the Kowloon
Kowloon is an urban area in Hong Kong comprising the Kowloon Peninsula and New Kowloon. It is bordered by the Lei Yue Mun strait in the east, Mei Foo Sun Chuen and Stonecutter's Island in the west, Tate's Cairn and Lion Rock in the north, and Victoria Harbour in the south. It had a population of...

 peninsular and the island of Hong Kong
Hong Kong
Hong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...

 itself. The distance that the ferry travels, as measured from passenger entrance to passenger entrance is 1007 m.

22.28707°N 114.16133°W Hong Kong (Central Star Ferry Pier)

22.29371°N 114.16803°W Kowloon (Tsim Sha Tsui Star Ferry Pier)

Central Park, Manhattan, New York City

Central Park
Central Park
Central Park is a public park in the center of Manhattan in New York City, United States. The park initially opened in 1857, on of city-owned land. In 1858, Frederick Law Olmsted and Calvert Vaux won a design competition to improve and expand the park with a plan they entitled the Greensward Plan...

 in New York City is 849 metres wide. It extends (roughly east and west) from Fifth Avenue to Eighth Avenue
Eighth Avenue (Manhattan)
Eighth Avenue is a north-south avenue on the West Side of Manhattan in New York City, carrying northbound traffic. Eighth Avenue begins in the West Village neighborhood at Abingdon Square and runs north for 44 blocks through Chelsea, the Garment District, Hell's Kitchen's east end, Midtown and the...

 (also known as Central Park West
Central Park West
Central Park West is an avenue that runs north-south in the New York City borough of Manhattan, in the United States....

). The distance between Eighth Avenue and Madison Avenue (one block east of Fifth Avenue) is 1011 metres. The width of the park is visible from many nearby skyscrapers and is walked daily by many people.

Suspension bridges

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A number of suspension bridges have a central span of a kilometre or more. The George Washington Bridge
George Washington Bridge
The George Washington Bridge is a suspension bridge spanning the Hudson River, connecting the Washington Heights neighborhood in the borough of Manhattan in New York City to Fort Lee, Bergen County, New Jersey. Interstate 95 and U.S. Route 1/9 cross the river via the bridge. U.S...

 in New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 (central span 1067 m) was the first bridge in the world to have a span of more than a kilometre and between 1931 and 1937, had the longest span of any bridge in the world. Other bridges that have a central span of about one kilometre include:
1030 m Third Kurushima-Kaikyo Bridge in Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

1020 m Second Kurushima-Kaikyo Bridge in Japan
1013 m Ponte 25 de Abril (Tagus Bridge) in Lisbon
Lisbon is the capital city and largest city of Portugal with a population of 545,245 within its administrative limits on a land area of . The urban area of Lisbon extends beyond the administrative city limits with a population of 3 million on an area of , making it the 9th most populous urban...

, Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

1006 m Forth Road Bridge
Forth Road Bridge
The Forth Road Bridge is a suspension bridge in east central Scotland. The bridge, opened in 1964, spans the Firth of Forth, connecting the capital city Edinburgh, at South Queensferry, to Fife, at North Queensferry...

 in Scotland
990 m Kita Bisan-Seto Bridge (Great Seto Bridge)
Kita Bisan-Seto Bridge
The is a suspension bridge with a center span of . It is the 19th largest suspension bridge in the world. The span carries roadway and the Seto-Ōhashi Line railway tracks. It is part of the Seto-Shuo Expressway and with the other five bridges along this route are collectively known as the...

 in Japan
988 m Severn Bridge
Severn Bridge
The Severn Bridge is a suspension bridge spanning the River Severn between South Gloucestershire, just north of Bristol, England, and Monmouthshire in South Wales, via Beachley, a peninsula between the River Severn and River Wye estuary. It is the original Severn road crossing between England and...

 linking England and Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

International usage

The United Kingdom and the United States are the only two developed countries which continue to use miles on road signs.

United Kingdom

In the United Kingdom, road signs show distances in miles and location marker posts
Driver location signs
Driver location signs are English highway route markers, first introduced in 2003, that complement distance marker posts. Both types of marker post display the distances from a nominal start point in kilometres...

 that are used for reference purposes by road engineers and emergency services show distance references in unspecified units which are kilometre-based.
The advent of the mobile phone has been instrumental in the English Department for Transport
Department for Transport
In the United Kingdom, the Department for Transport is the government department responsible for the English transport network and a limited number of transport matters in Scotland, Wales and Northern Ireland which are not devolved...

 authorising the use of driver location signs
Driver location signs
Driver location signs are English highway route markers, first introduced in 2003, that complement distance marker posts. Both types of marker post display the distances from a nominal start point in kilometres...

 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. The Executive Director of the US Federal Highway Administration
Federal Highway Administration
The Federal Highway Administration is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two "programs," the Federal-aid Highway Program and the Federal Lands Highway Program...

, 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
United States Department of Transportation
The United States Department of Transportation is a federal Cabinet department of the United States government concerned with transportation. It was established by an act of Congress on October 15, 1966, and began operation on April 1, 1967...

] 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." The Manual on Uniform Traffic Control Devices
Manual on Uniform Traffic Control Devices
The Manual on Uniform Traffic Control Devices is a document issued by the Federal Highway Administration of the United States Department of Transportation to specify the standards by which traffic signs, road surface markings, and signals are designed, installed, and used...

 since 2000 is published in both metric and American Customary Units. (See also Metrication in the United States
Metrication in the United States
Metrication is the process of introducing the International System of Units , a metric system of measurement, to replace the historical or customary units of measurement of a country or region...


Covering one kilometre

The time taken to cover a kilometre is dependent on one's speed. Walking on flat ground, a hiker can expect to cover one kilometre in 12 minutes
while a car travelling at a speed of 120 kilometre per hour — the speed limit in many European countries — will cover a kilometre in 30 seconds.

Some sporting disciplines feature 1000 m (one kilometre) races in major events (such as the Olympic Games
Olympic Games
The Olympic Games is a major international event featuring summer and winter sports, in which thousands of athletes participate in a variety of competitions. The Olympic Games have come to be regarded as the world’s foremost sports competition where more than 200 nations participate...

), 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 Location Year Comments
Running (M) Noah Ngeny
Noah Ngeny
Noah Kiprono Ngeny is a former Kenyan athlete, Olympic gold medalist at 1500 m at the 2000 Summer Olympics, and world record holder in the 1000 m.-Before Sydney:...

2:11.96 Rieti, Italy 5 September 1999 Not an Olympic event
Running (F) Svetlana Masterkova
Svetlana Masterkova
Svetlana Alexandrovna Masterkova is a Russian former middle distance runner and current world record holder for the mile. At the 1996 Summer Olympics, she won the gold medal in both the 800 and 1,500 metres....

2:28.98 Brussels
Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...

23 August 1996 Not an Olympic event
Speed Skating
Speed skating
Speed skating, or speedskating is a competitive form of ice skating in which the competitors race each other in traveling a certain distance on skates. Types of speed skating are long track speed skating, short track speed skating, and marathon speed skating...

Shani Davis
Shani Davis
Shani Davis is an Olympic Champion speed skater from the United States.At the 2006 Winter Olympics in Turin, Italy, Davis became the first Black athlete to win a gold medal in an individual sport at the Olympic Winter Games . He also won the silver in the 1,500 m...

1:06.42 Salt Lake City 7 March 2009
Speed Skating
Speed skating
Speed skating, or speedskating is a competitive form of ice skating in which the competitors race each other in traveling a certain distance on skates. Types of speed skating are long track speed skating, short track speed skating, and marathon speed skating...

Cindy Klaasen 1:13.11 Calgary
Calgary is a city in the Province of Alberta, Canada. It is located in the south of the province, in an area of foothills and prairie, approximately east of the front ranges of the Canadian Rockies...

25 March 2006
Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...

Arnaud Tourant 58.875 s La Paz, Bolivia 10 October 2001 No offical 1000m woman's record

See also

  • Conversion of units
    Conversion of units
    Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.- Process :...

    , for comparison with other units of length
  • Cubic kilometre
  • Orders of magnitude (length)
  • SI prefix
    SI prefix
    The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...

  • Square kilometre
    Square kilometre
    Square kilometer, symbol km2, is a decimal multiple of the SI unit of surface area, the square metre, one of the SI derived units.1 km2 is equal to:* 1,000,000 m2* 100 ha * 0.386302 square miles* 247.105381 acresConversely:...

  • 1 kilometre
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