Miles per hour

Automobile speedometer, indicating speed in miles per hour on the outer track and kilometres per hour on the inner track

Miles per hour is an imperial unit of speed expressing the number of statute miles covered in one hour. While kilometres per hour is more commonly used worldwide, mph remains the standard unit used for speed limits in some countries, and to express speeds generally, in many countries throughout the world.

These include roads in the United Kingdom, the United States,^[1][2] American Samoa,^[3] the Bahamas,^[4] Belize,^[5] British Virgin Islands,^[6] the Cayman Islands,^[7] Dominica,^[8] the Falkland Islands,^[9] Grenada,^[10] Guam,^[11] Myanmar,^[12] The N. Mariana Islands,^[13] Samoa,^[14] St. Lucia,^[15] St. Vincent & The Grenadines,^[16] St. Helena,^[17] St. Kitts & Nevis,^[18] Turks & Caicos Islands,^[19] the U.S. Virgin Islands,^[20][21] Antigua & Barbuda (although km are used for distance),^[22] and Puerto Rico (same as former).^[23]

Miles per hour are also used in the Canadian rail system.^[24] In some countries it may be used to express the speed of delivery of a ball in sporting events such as cricket, tennis, and baseball. A common abbreviation is mph or MPH.

Road traffic speeds in other countries are quoted in km/h. Occasionally, however, both systems are used: for example, in Ireland, a judge considered a speeding case by examining speeds in both kilometres per hour and miles per hour. The judge was quoted as saying the speed seemed "very excessive" at 180 km/h but did not look "as bad" at 112 mph; a reduced fine was still imposed on the speeding driver.^[25] In addition, there are two examples of km and MPH used side by side above.

Nautical and aeronautical applications, however, favour the knot as a common unit of speed: one knot is one nautical mile per hour.

Conversions

1 mph	= 0.44704 m/s (exactly)
	= 1.609344 km/h (exactly)
	= 1.46 ft/s (exactly)
	≈ 0.868976 kn

See also

• Acceleration
• Kilometres per hour
• Light-year
• Orders of magnitude (speed)
• Velocity

References