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| SI units | |
|---|---|
| 1.609344 km | 1,609.344 m |
| US customary / Imperial units | |
| 1,760 yd | 5,280 ft |
"Miles" redirects here. For other uses, see Miles (disambiguation).
A mile is a unit of length, usually used to measure distance, in a number of different systems, including Imperial units, United States customary units and Norwegian/Swedish mil. Its size can vary from system to system, but in each is between one and ten kilometers. In contemporary English contexts, mile refers to either of the following:
There have been several abbreviations for mile (with and without trailing period): mi, ml, m, M. In the United States, the National Institute of Standards and Technology now uses and recommends mi Tina Butcher et al. ed. (2007) Appendix C, p. C-13. but in everyday usage (at least in the United States and in the United Kingdom) usages such as miles per hour and miles per gallon are almost always abbreviated as mph or mpg (rather than mi/h or mi/gal).
The formula "multiply by 8 and divide by 5" to convert international miles to kilometers gives a conversion of 1.6, accurate to 0.6%, which is a useful approximation.
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The unit of distance mille passus (literally "a thousand paces" in Latin, with one pace being equal to two steps) was first used by the Romans and denoted a distance of 1,000 paces or 5,000 Roman feet, and corresponded to about 1,480 meters, or 1,618 modern yards. This unit is now known as the Roman mile.Smith, 762
The current definition of a mile as 5,280 feet (as opposed to 5,000) dates to the 13th century, and was confirmed by statute in the reign of Queen Elizabeth I;Klein (1974, corrected 1988), 69. However, various English-speaking countries maintained independent length standards for the yard, which differed by small but measurable amounts, and thus led to miles of slightly different lengths. This was resolved in 1959 with the definition of the current international mile by Australia, Canada, New Zealand, South Africa, the United Kingdom, and the United States.Louis E. Barbrow and Lewis V. Judson, (1976), 16, 17, 20.
In modern usage, various distances are referred to as miles.
The international mile (and before 1959, the statute mile) is the distance typically meant when the word mile is used without other qualifying words (e.g. nautical mile, see below). The international and statute miles are all equal to 5,280 feet, but the international mile is defined in terms of the international foot, while the statute miles of the various English-speaking countries were based on the national foot of each country. The (mostly obsolete) U.S. statute mile is based on the U.S. survey foot (which is exactly 1200/3937 m) and differs from the international mile by about 3 mm. Tina Butcher et al. ed. (2007), Appendix C, p. C-13, footnote 11.
The name statute mile originates from a Statute of the Parliament of England in 1592 during the reign of Elizabeth I. This defined the Statute Mile as 5,280 ft or 1,760 yards; or 63,360 inches. Both statute and international miles are divided into eight furlongs (the length generally that a furrow was ploughed before the horses were turned, furlong = furrow-long). In turn a furlong is ten chains (a surveyor\'s chain, used as such until laser range finders took over); a chain is 22 yards and a yard is three feet, making up 5,280 ft.
Before the statute of the English parliament, there was confusion on the length of the "mile". The Irish mile was 6,721 feet and the Scottish mile was 5,951 feet. Klein (1974 corrected 1988), 70. Perhaps the earliest tables of English linear measures, Arnold\'s Customs of London (c. 1500) indicates a mile consisted of 8 furlongs, each of 625 feet, for a total of 5,000 feet. Klein, (1974 corrected 1988), 69. For other "miles" see the list below.
On the utility of the nautical mile
Each circle shown is a great circle – the analog of a line in spherical trigonometry – and hence the shortest path connecting two points on the globular surface.
The nautical mile was originally defined as one minute of arc along a meridian (or in some instances any great circle) of the Earth.Maloney, (1978), 34. Although this distance varies depending on the latitude of the meridian (or great circle) where it is used, on average it is about 6,076 feet (about 1852 meters or 1.15 statute miles).
The nautical mile per hour is known as the knot.
Navigators use dividers to step off the distance between two points on the nautical chart, then place the open dividers against the minutes-of-latitude scale at the edge of the nautical chart, and read off the distance in nautical miles.Maloney, (1978), 34–35. Since it is now known that the Earth is an ellipsoid (oblate spheroid), not a sphere, the distance of nautical miles derived from this method varies from the equator to the poles. For instance, using the WGS84 Ellipsoid, the commonly accepted Earth model for many purposes today, one minute of latitude at the WGS84 equator is 6,087 feet and at the poles is 6,067 feet.
In the United States of America, the nautical mile was defined in the nineteenth century as 6,080.2 feet (1,853.249 m), whereas in the United Kingdom the Admiralty nautical mile was defined as 6,080 feet (1,853.184 m) and was approximately one minute of latitude in the latitudes of the south of the UK. Other nations had different definitions of the nautical mile, but it is now internationally defined to be exactly 1,852 meters.
The nautical mile is almost universally used for navigation in aviation, maritime, and nautical roles because of its relationship with degrees and minutes of latitude and the ability to use the latitude scale of a map for distance measuring.
Even in countries that have moved from the Imperial to the Metric system (for example, Australia and New Zealand), the mile is still used in a variety of idioms. These include:
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