Units of speed
Road speeds are given in km/h in most countries and in mph (miles per hour) in the US and UK. In physics the base unit is m/s, and ships and aircraft use knots (kn), which are nautical miles per hour.
Handy reference points
1 m/s = 3.6 km/h, 1 mph is exactly 1.609344 km/h and 1 knot is exactly 1.852 km/h. For quick estimates, 100 km/h is about 62 mph and 60 mph is about 97 km/h. A Mach number is a multiple of the speed of sound, about 340 m/s at sea level and 15 °C.
Conversion factors
1 km/h = 0.621371 mph
1 mph = 1.60934 km/h
One unit converted to all others: Kilometer per hour (km/h)
| Unit | Value |
|---|---|
| Meter per second (m/s) | 0.277778 |
| Kilometer per hour (km/h) | 1 |
| Mile per hour (mph) | 0.621371 |
| Knot (kn) | 0.539957 |
| Foot per second (ft/s) | 0.911344 |
| Kilometer per second (km/s) | 0.000277778 |
| Mach | 0.000816297 |
Common values
| Kilometer per hour (km/h) | Mile per hour (mph) |
|---|---|
| 1 km/h | 0.621371 mph |
| 5 km/h | 3.10686 mph |
| 10 km/h | 6.21371 mph |
| 50 km/h | 31.0686 mph |
| 100 km/h | 62.1371 mph |
| Mile per hour (mph) | Kilometer per hour (km/h) |
|---|---|
| 1 mph | 1.60934 km/h |
| 5 mph | 8.04672 km/h |
| 10 mph | 16.0934 km/h |
| 50 mph | 80.4672 km/h |
| 100 mph | 160.934 km/h |