Speed Converter
Convert between km/h, mph, knots and metres per second, with the formula shown for each conversion.
How speed conversion works
Every unit here is defined against metres per second. Converting means dividing by the source unit's factor and multiplying by the target unit's factor, the same base-unit method used by every converter on this site.
The one to remember: 100 km/h is about 62.14 mph, since 1 mph is exactly 1.609344 km/h.
Reference points
| km/h | mph | m/s |
|---|---|---|
| 50 km/h | 31.07 mph | 13.89 m/s |
| 100 km/h | 62.14 mph | 27.78 m/s |
| 120 km/h | 74.56 mph | 33.33 m/s |
| 1.852 km/h | 1.151 mph | 1 knot |
What a knot actually is, and why it differs from mph
A knot is one nautical mile per hour, not one statute mile per hour. The nautical mile (1,852 metres exactly) was originally defined as one minute of latitude along a meridian, which is why ships and aircraft use it: a distance in nautical miles maps directly onto a distance on a navigation chart. The statute mile behind mph (1,609.344 metres) has no such geographic meaning; it comes from Roman and English land-measurement history instead.
Because the nautical mile is about 15% longer than the statute mile, 1 knot equals about 1.151 mph, not 1 mph. Wind speed, boat speed and aircraft airspeed are given in knots for exactly this reason: the same navigation charts and flight-planning tools were built around nautical miles.