Miles per hour

"MPH" redirects here. For other uses, see MPH (disambiguation).

Automobile speedometer, measuring 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. It is currently the standard unit used for speed limits, and to express speeds generally, on roads in the United Kingdom and the United States.^[1][2] It is also often used to express the speed of delivery of a ball in various sporting events, such as cricket, tennis, and baseball. A common abbreviation is mph or MPH.

In the International System of Units (SI), the basic unit of speed or velocity is m/s. Road traffic speeds in most 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.^[3]

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 is equal to:

• 0.44704 m/s, the SI derived unit
• 1.609344 km/h
• 1.4667 feet per second (= 22/15 feet per second)
• approx. 0.868976 knots

When converting miles per hour to another unit of measurement, or vice versa, it helps to know exactly how miles and hours are related to other units of distance and time, respectively. For example, 1 mile is equal to 5,280 feet, 1,760 yards, or 1,609.344 metres. Likewise, 1 hour is equal to 60 minutes, or 3,600 seconds.

Conversions between common units of speed

	m/s	km/h	mph	knot	ft/s
1 m/s =	1	3.6	2.236936	1.943844	3.280840
1 km/h =	0.277778	1	0.621371	0.539957	0.911344
1 mph =	0.44704	1.609344	1	0.868976	1.466667
1 knot =	0.514444	1.852	1.150779	1	1.687810
1 ft/s =	0.3048	1.09728	0.681818	0.592484	1

(Values in bold face are exact.)

See also

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

References

1. ^ Speed limit signs (UK) Department for Transport. Retrieved 14 September 2011
2. ^ "Modern Living: Think Metric". Time Magazine. June 09, 1975. http://www.time.com/time/magazine/article/0,9171,913145,00.html. Retrieved 2010-06-15. "Meanwhile, the metricization of America is already taking place. Individual federal agencies, school systems, states and industries, as well as radio announcers, supermarkets, beverage bottlers and ballpark scoreboards, are hastening the everyday use of meters, liters and grams. ...a road sign outside Fergus Falls reads, ST. CLOUD 100 MILES OR 161 KILOMETERS. Other signs note that 55 m.p.h. equals 88 kilometers per hour." 
3. ^ The Associated Press (November 1, 2007). "Another Metric System Fault". The New York Times. http://query.nytimes.com/gst/fullpage.html?res=9400E1D61438F932A35752C1A9619C8B63. Retrieved 1 November 2010.