Speed converters
Convert speeds between miles per hour and kilometers per hour.
About speed conversion
Speed is distance over time, so its units inherit the metric–imperial split of distance: kilometers per hour where roads are metric, miles per hour in the United States and United Kingdom, meters per second in science and engineering, knots at sea and in the air. The conversions are exact because the underlying distances are: one mile is 1.609344 km, one hour is 3 600 seconds.
Conversion factors at a glance
| Unit | Equals |
|---|---|
| 1 km/h | 0.6214 mph = 0.2778 m/s = 0.54 knots |
| 1 mph | 1.609 km/h = 0.447 m/s = 0.869 knots |
| 1 m/s | 3.6 km/h = 2.237 mph |
| 1 knot | 1.852 km/h = 1.151 mph |
Which converter do I need?
Driving abroad. Miles per hour to kilometers per hour and back, for speed limits and rental-car speedometers. Physics, wind and sport science. Kilometers per hour to meters per second and back — the unit needed for braking distance, kinetic energy and Beaufort wind tables.
Reference speeds
A brisk walk is 5 km/h (3 mph, 1.4 m/s). City traffic runs at 50 km/h (31 mph). A motorway limit of 120 km/h is 75 mph or 33 m/s. A sprinter peaks near 44 km/h (27 mph, 12 m/s). Sound travels at 1 235 km/h (767 mph, 343 m/s) at sea level.
Common questions
How fast is 100 km/h in mph? 62 mph. What is 70 mph in km/h? 113 km/h. How many m/s is 100 km/h? 27.8 m/s. What is the speed of sound? 343 m/s, 1 235 km/h, 767 mph at sea level. How fast does a person walk? About 5 km/h, 3 mph, 1.4 m/s.