Speed converter
Convert speed between m/s, km/h, mph and knots. Example: 100 km/h is 62.137119 mph; 20 m/s is 72 km/h; 10 knots is about 18.52 km/h.
What to know
The speed page covers four units: metres per second, kilometres per hour, miles per hour and knots. Values pass through m/s using 1 km/h = 1/3.6 m/s, 1 mph = 0.44704 m/s and 1 knot = 0.514444 m/s.
Worked examples: 100 km/h to mph is (100 / 3.6) / 0.44704 = 62.137119 mph, and 20 m/s to km/h is 20 x 3.6 = 72 km/h. A ship making 10 knots covers 10 x 0.514444 x 3.6 = 18.519984 km/h.
The knot factor is the rounded 0.514444 rather than the exact 1852/3600, so results differ from an exact nautical conversion only in the sixth decimal place. That is far below any practical need for sailing or flight planning.
The default pair is m/s to km/h. It is the conversion most people need for wind speeds in weather bulletins, running paces on a treadmill display and speed limits between metric and imperial countries.
For running and cycling, 12 km/h is 7.456454 mph, and a pace of 3.333333 m/s equals 12 km/h. Wind speeds in forecasts often come in m/s while road signs use km/h or mph, so one tool covers all three.
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How to use Speed converter
- Type 100 in the Value field.
- Select km/h in From and mph in To.
- Read the Result line, which shows 62.137119 mph.
- Change From to knot and enter 10 to see 18.519984 km/h.
Quick answers
What is 70 mph in km/h?
About 112.654 km/h, from 70 x 0.44704 x 3.6. Pick mph to km/h and type 70.
How fast is 1 m/s in km/h?
Exactly 3.6 km/h, because there are 3,600 seconds in an hour and 1,000 metres in a kilometre.
Is a knot the same as mph?
No. One knot is a nautical mile per hour, about 1.15078 mph, so 20 knots corresponds to roughly 23 mph.