Mile per Hour (mph)
Definition
Miles per hour (symbol mph) is a unit of speed in the imperial and US customary systems equal to exactly 0.44704 meters per second. It is the standard unit on speedometers and road signs in the United States and the United Kingdom.
History
Miles per hour emerged in the 19th century as steam locomotives and later automobiles made sustained measured speed a public concern. By the early 20th century mph dominated English-speaking road and rail signage and stayed there even after most Commonwealth countries switched to kilometers per hour.
The unit is defined relative to the international mile (1,609.344 m) and the hour (3,600 s). The U.S. and U.K. continue to display vehicle speeds and posted limits in mph, while most of the rest of the world uses km/h.
Standard reference
Defined as 1 international mile / 1 hour = 1,609.344 m / 3,600 s = 0.44704 m/s exactly. Used by the U.S. Federal Highway Administration on the Manual on Uniform Traffic Control Devices.
Common conversions
| 1 mph | = 1.609344 km/h |
|---|---|
| = 0.44704 m/s | |
| = 1.46667 ft/s | |
| = 0.868976 kn |