Kilometers
Abbreviation/Symbol:
Km
Slang: ‘k’ or ‘kays’ – spoken
Unit of:
Worldwide use:
The kilometre is used worldwide as a unit used for expressing distances between geographical locations on land, and in most countries is the official unit for this purpose. Primary exceptions are the United Kingdom and the United States of America, where miles are more commonly used.
A kilometer (km) is 1,000 meters, or 0.621 miles. 10km is 6.21 miles.
Road signs, speed limits and map distances are given in kilometers in most countries, and athletics races such as the 5km and 10km are named for them. The marathon is 42.195km.
Definition:
The kilometre is unit of length in the metric system equivalent to one thousand metres.
1Km is equivalent to 0.6214 miles.
The kilo- in kilometer is the same prefix as in kilogram and always means a thousand. Since the meter is now defined from the speed of light, a kilometer is the distance light travels in a vacuum in 1/299,792.458 of a second.
Origin:
The metric, or decimal, system of weights and measures was adopted in France in 1795. Using the metre as the basis for length measurements, the system is now used officially across the globe, with a few notable exceptions.
The kilometer dates from the French Revolution, when the Academy of Sciences set up a committee in 1790 to replace France's many local measures with one rational system.
The committee proposed a decimal-based system known as the metric system. This system aimed to establish a consistent set of units that would be based on natural phenomena and easily divisible by powers of ten. The astronomers Jean-Baptiste Joseph Delambre and Pierre Méchain carried out the survey of the meridian from Dunkirk to Barcelona between 1792 and 1798 to measure the meter.
One of the fundamental units of this new system was the meter, which was defined as one ten-millionth of the distance from the North Pole to the equator along a meridian passing through Paris. The kilometer, derived from the meter, was defined as one thousand meters. This unit was chosen to represent longer distances, such as those encountered in land surveys and transportation.
France adopted the metric system in 1795, and it spread to most other countries over the next two centuries, kilometer included. The US and UK are the main exceptions, still using miles on road signs.
Common references:
The world’s tallest building, Burk Khalifa in Dubai, is 0.82984km tall.
Niagara Falls, on the U.S.A./Canada border, is approximately 1Km across
The peak of Mount Everest is 8.848Km above sea level.
Paris in France is 878Km from Berlin in Germany, although you would have to make a journey of over 1050Km to travel from one to the other by land transport.
The average distance from Earth to the Moon is 384,400Km.
Usage context:
The kilometre is used worldwide as a unit used for expressing distances between geographical locations on land, and in most countries is the official unit for this purpose. Primary exceptions are the United Kingdom and the United States of America.
The kilometre is most commonly used on road signs to denote the distance left to travel to a given location. It is also the most popular unit for describing the distance between two locations in a straight line (across the surface of the Earth).
Multiples:
Units of length/distance in the metric scale are based on fractions or multiples of one metre, thus there are no official multiples of the kilometre. However, there are metric measurements of length/distance greater than a kilometre that can be expressed in terms of kilometres.
A megameter = 1 million metres (or 10,000Km)
A gigametre = 1 billion metres (or 1,000,000Km)