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{{Infobox unit
| bgcolor      = 
| name         = Mile
| standard     = [[English units of measurement|English unit]]
| quantity     = length
| symbol       = mi
| symbol2      = m
| units1       = [[SI units]]
| inunits1     = {{val|1609.344|ul=m}}
| units2       = [[imperial units|imperial]]/[[US customary units|US]]&nbsp;units
| inunits2     = {{ubl|{{val|63360|ul=inches}}|{{val|5280|ul=feet}}|{{val|1760|ul=yards}}|80 [[chain (unit)|ch]]}}
| units3       = nautical&nbsp;units
| inunits3     = {{convert|1|mi|nmi|disp=out|lk=on|sigfig=5|comma=gaps}}
}}
{{Redirect|Miles}}

A '''mile''' is a [[Units of measurement|unit]] of [[length]], usually used to measure [[distance]], in a number of different systems, including [[Imperial unit]]s, [[United States customary units]] and [[Norwegian/Swedish mil]]. Its size can vary from system to system, but in each is between one and fifteen [[kilometer]]s. In contemporary English contexts, ''mile'' most commonly refers to the ''international mile'' of 5,280&nbsp;[[Feet (unit of length)|feet]], 1,760&nbsp;[[yard]]s, or exactly 1,609.344&nbsp;[[metre|meters]].  Other English-language phrases involving mile include:
* the ''U.S. survey mile'' of 5,280 [[survey foot|survey feet]] which is slightly longer at approximately 1,609.347219 meters (1 international mile is exactly 0.999998 survey mile).<ref>A. V. Astin & H. Arnold Karo, (1959) Using values in this document, international yard divided by former U.S. yard is (9144×3937)/(3600×10000) = 499999/500000 = 0.999998 exactly.</ref><ref>Tina Butcher et al. ed. (2007), Appendix C, p. C-13, footnote 11.</ref>

* the ''[[#International and statute miles|statute mile]]'' in popular usage is any mile of 5,280 feet, regardless of the precise definition of the foot used.

* the international ''[[nautical mile]]'' of 1,852&nbsp;[[meters]] (about 6,076&nbsp;[[Feet (unit of length)|feet]]).<ref>[http://www.bipm.org/en/si/si_brochure/chapter4/table8.html Section 4.1 Table 8] in the ''International System of Units'' 8th ed. (2006) by the [[Bureau International des Poids et Mesures]].</ref>

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''<ref>
Tina Butcher et al. ed. (2007) Appendix C, p. C-13.</ref> 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.

== Historical definitions ==
The unit of distance ''{{lang|la|mille passus}}'' (literally "a thousand [[paces]]" in Latin, with one pace being equal to two steps) was first used by the [[Ancient Rome|Romans]] and denoted a distance of 1,000&nbsp;paces or 5,000&nbsp;Roman&nbsp;feet, and corresponded to about 1,480&nbsp;meters, or 1,618&nbsp;modern&nbsp;yards. This unit is now known as the '''Roman mile'''.<ref>Smith, 762</ref>

The current definition of a mile as 5,280&nbsp;feet (as opposed to 5,000) dates to the 13th century, and was confirmed by statute in the reign of [[Elizabeth I of England|Queen Elizabeth I]];<ref>Klein (1974, corrected 1988), 69.</ref> 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.<ref>Louis E. Barbrow and Lewis V. Judson, (1976), 16, 17, 20.</ref>

== Types of mile ==
In modern usage, various distances are referred to as ''miles''.

=== International and statute 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 both equal to 5,280 feet, but the international mile is defined in terms of the international foot (0.3048&nbsp;m), while the statute miles of the various English-speaking countries were based on the national foot of each country. In the U.S., in popular usage no distinction is made among mile, international mile, and statute mile<ref>American Heritage Dictionary (1993) s.v. mile and statute mile.</ref> but the [[National Institute of Standards and Technology]] asserts the statute mile is based on the U.S. survey foot (which is exactly 1200/3937&nbsp;m) and differs from the international mile by about 3&nbsp;mm. <ref>Tina Butcher et al. ed. (2007), Appendix C, p. C-13, footnote 11.</ref>

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&nbsp;ft or 1,760&nbsp;yards; or 63,360&nbsp;[[inch]]es. Both statute and international miles are divided into eight [[furlong]]s (the length generally that a furrow was ploughed before the horses were turned, furlong = furrow-long). In turn a furlong is ten [[Chain (unit)|chains]] (a surveyor's chain, used as such until laser range finders took over); a chain is 22&nbsp;yards and a yard is three feet, making up 5,280&nbsp;ft.

=== Other miles in Britain and Ireland ===
Before the statute of the English parliament, there was confusion on the length of the "mile". The Irish mile was 6,721&nbsp;feet and the Scottish mile was 5,951&nbsp;feet.<ref> Klein (1974 corrected 1988), 70.</ref> 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.<ref> Klein, (1974 corrected 1988), 69.</ref> For other "miles" see the list below.

=== Nautical miles ===
[[Image:RechtwKugeldreieck.svg|thumb|150 px|right|'''On the utility of the nautical mile'''<br>Each circle shown is a [[great circle]] &ndash; the analog of a line in spherical trigonometry &ndash; and hence the shortest path connecting two points on the globular surface. Meridians are great circles that pass through the poles.]]
{{main|Nautical mile}}

The '''nautical mile''' was originally defined as one [[minute]] of [[Arc (geometry)|arc]] along a [[Meridian (geography)|meridian]] of the Earth.<ref>Maloney, (1978), 34.</ref> It is a convenient reference since it is fairly constant at all latitudes, in contrast with degrees of longitude which vary from 1&nbsp;NM at the equator to zero at the poles.

Navigators use dividers to step off the distance between two points on the navigational chart, then place the open dividers against the minutes-of-latitude scale at the edge of the chart, and read off the distance in nautical miles.<ref>Maloney, (1978), 34&ndash;35.</ref> Since it is now known that the Earth is not perfectly spherical but an oblate spheroid, the length derived from this method varies slightly from the equator to the poles. For instance, using the [[World Geodetic System|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. On average it is about 6,076&nbsp;feet (about 1852&nbsp;[[metre|meters]] or 1.15&nbsp;[[statute miles]]). 

In the [[United States of America]], the nautical mile was defined in the nineteenth century as 6,080.2&nbsp;feet (1,853.249&nbsp;m), whereas in the [[United Kingdom]] the '''Admiralty nautical mile''' was defined as 6,080&nbsp;feet (1,853.184&nbsp;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&nbsp;meters.

The nautical mile per hour is known as the '''[[knot (speed)|knot]]'''. Nautical miles and knots are almost universally used for aeronautical and maritime navigation because of their relationship with degrees and minutes of latitude and the convenience of using the latitude scale on a map for distance measuring.

== Other miles ==
* The Danish ''{{lang|da|mil}}'' (traditional) was 24,000 Danish feet or 7.5325 kilometers. Sometimes it was interpreted as exactly 7.5 kilometers. It is the same as the north German ''{{lang|de|Meile}}'' (below).<ref>Rowlett (2005).  s.v. mil [4].</ref>
* The [[data mile]] is used in [[radar]]-related subjects and is equal to 6,000 [[foot (unit of length)|feet]] (1.8288 [[kilometer]]s).<ref>Rowlett (2005). s.v. data mile.</ref>
* The ''{{lang|de|Meile}}'' was a traditional unit in German speaking countries, much longer than a western European mile. It was 24,000 German feet; the SI equivalent was 7586 meters in Austria or 7532.5 meters in northern Germany. There was a version known as the ''{{lang|de|geographische Meile}}'' which was 4 Admiralty nautical miles, 7,412.7 meters, or 1/15 degree.<ref>Rowlett (2005), s.v meile.</ref>
* The term [[metric mile]] is used in sports such as [[athletics (track and field)]] and [[speed skating]] to denote a distance of 1.5&nbsp;[[kilometer]]s. In United States high school competition the term is sometimes used for a race of 1.6&nbsp;kilometers.<ref> Rowlett (2005). s.v. mile.</ref>
* In Norway and Sweden a ''{{lang|no|mil}}'' is a unit of length which is equal to 10 kilometers and commonly used in everyday language. However in more formal situations, like on road signs and when there is risk of confusion with English miles, kilometers are used instead. The traditional Swedish ''{{lang|sv|mil}}'' spanned the range from 6000-14,485 meters, depending on [[provinces of Sweden|province]]. It was however standardized in 1649 to 36,000 Swedish feet, or 10.687 kilometers<ref>Rowlett (2005). s.v. mil [4].</ref>. The Norwegian ''{{lang|no|mil}}'' was 11.298 kilometers. When the metric system was introduced in the [[Union between Sweden and Norway|Norwegian-Swedish union]] in 1889, one standardized the ''{{lang|no|mil}}'' to exactly 10 kilometers <ref>Rowlett (2005). s.v. mil [4].</ref>

* The ''radar mile'' is a unit of time, equal to the time required for a radar pulse to travel a distance of two miles (one mile each way). Thus, the radar statute mile is 10.8&nbsp;μs and the radar nautical mile is 12.4&nbsp;μs.<ref>Rowlett (2005). s.v. radar mile.</ref>
* The Russian {{lang|ru|''milya'' (русская миля)}} was a [[Obsolete Russian weights and measures|traditional Russian unit]] of distance, equal to 7 ''[[Versta|verst]]'', or 7.468 km
* The ''{{lang|hr|hrvatska milja}}'' (Croatian mile) is 11,130 metres = 11.13 kilometres = 1/10 of equator's degree.<ref>{{in lang|hr}} [http://public.carnet.hr/zuh/do1874/nv17/nv17_11.htm Centuries of Natural Science in Croatia : Theory and Application] Kartografija i putopisi </ref>, first time used by [[Jesuit]] [[Stjepan Glavač]] on map from 1673.
* The ''{{lang|hr|banska milja}}'' (also called ''{{lang|hr|hrvatska milja}}'') (mile of Croatian [[ban (title)|Ban]], Croatian mile) was 7586 metres=7,586 kilometres, or 24,000 feet.<ref>{{in lang|hr}} [http://www.matica.hr/Vijenac/vij232.nsf/AllWebDocs/opacic Vijenac] Mrvice s banskoga stola </ref>.

== Idioms == 
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:
* A ''[[wikt:country mile|country mile]]'' is used [[colloquial]]ly to denote a very long distance.
* ''"A miss is as good as a mile"'' (Failure by a narrow margin is no better than any other failure)
* ''"Give him an inch and he'll take a mile"'' (The person in question will become greedy if shown generosity)
* ''"Missed by a mile"'' (Missed by a wide margin)
* ''"Talk a mile a minute"'' (Speak at a rapid rate)
* ''"To go the extra mile"'' (To put in extra effort)
* ''"Miles away"'' (Lost in thought, or daydreaming)

== See also ==
{{colbegin|colwidth=18em}}
*[[Anthropic units]]
*[[Fibonacci sequence]] for miles converting to [[kilometers]]
*[[Four-minute mile]]
*[[Geographical mile]]
*[[Imperial unit]]s
*[[League (unit)|League]]
*[[wikt:Roman mile|Roman mile]]
*[[Square mile]]
*[[Systems of measurement]]
*[[U.S. customary units]]
{{colend}}

== Notes ==
{{reflist}}

== References ==
*''American Heritage Dictionary of the English Language'' (3rd ed.) (1992). Boston: Houghton Mifflin Company.

*Astin. V. and [[Henry Arnold Karo|H. Arnold Karo]]. (1959). [http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf ''Refinement of values for the yard and the pound,''] Washington DC: National Bureau of Standards, republished on  National Geodetic Survey web site and the Federal Register (Doc. 59-5442, Filed, June 30, 1959, 8:45 a.m.)

*Barbrow, Louis E. and Lewis V. Judson (1976). [http://physics.nist.gov/Pubs/SP447/ ''Weights and Measures Standards of the United States: a brief history'']. [[National Institute of Standards and Technology]].

*Butcher, Tina et al. ed. (2007). [http://ts.nist.gov/WeightsAndMeasures/h44-07.cfm ''NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices.''] Appendix C, p. C-13.

*Klein, Herbert Arthur (1974, corrected 1988). ''The Science of Measurement: A Historical Survey''. New York: Dover. (previously published by Simon & Schuster under the title ''The World of Measurements: Masterpieces, Mysteries and Muddles of Metrology)

*Maloney, Elbert S. (1978). ''Dutton's Navigation and Piloting''. 13th Ed. Annapolis: Naval Institute Press.

* Rowlet, Russ (2005). [http://www.unc.edu/~rowlett/units/index.html ''How Many? A Dictionary of Units of Measurement'']. Faculty member's web page at [[University of North Carolina at Chapel Hill]]. Accessed 2007-11-10.

*{{cite book
  | last = Smith
  | first = William
  | title = Dictionary of Greek and Roman Antiquities
  | publisher = John Murray
  | date = 1875
  | location = London
  | pages = 762
}}

== External links ==
* [http://ts.nist.gov/WeightsAndMeasures/Publications/appxc.cfm NIST General Tables of Units of Measurement]