Speed Converter
Convert a speed between kilometers per hour, miles per hour, meters per second, feet per second and knots. The factor line shows the exact number used, so you can redo the arithmetic by hand.
Exact factors: 1 mph = 1.609344 km/h, 1 m/s = 3.6 km/h, 1 ft/s = 0.3048 m/s, 1 kn = 1.852 km/h.
Formula and calculation
Worked example
A sprinter running 10 m/s: multiply by 3.6 and the speed is 36 km/h. The factor line reads 1 m/s = 3.6 km/h — one meter per second is exactly 3.6 kilometers per hour, the one conversion worth remembering.
Knots, Mach and the units that need context
A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 m, so 1 kn = 1.852 km/h with no rounding anywhere. Aviation and shipping still use it because a nautical mile equals one minute of latitude, which makes distance and speed on a chart the same number. Mach is a different kind of unit: it is a ratio to the local speed of sound, and that speed falls as the air gets colder. Sound travels about 343 m/s at 20 °C near sea level, roughly Mach 1 = 1,235 km/h, but only about 295 m/s at 36,000 ft where the air is near −54 °C. A Mach number without a temperature and altitude means very little, which is why it is not one of the units here.
What the results mean
- 1 mph =
- Your speed in the target unit, converted with exact factors — 1 mph is 1.609344 km/h and 1 knot is 1.852 km/h, both exact.
- Conversion factor
- The one-way factor for this pair, so you can repeat the arithmetic by hand: value x factor = result.
- Reverse
- The same factor in the opposite direction, for converting a result back later.
Frequently asked questions
How many km/h is 100 mph?
Exactly 160.9344, because the mile is defined as 1.609344 km. Going the other way, 100 km/h is 62.1371 mph — worth knowing, since 60 mph and 100 km/h are close but not the same.
What is a knot in mph?
One knot is 1.852 km/h, which is 1.150779 mph. Ships and aircraft report knots because a nautical mile is one minute of latitude, so speed in knots is also distance in nautical miles per hour on a chart.
How do I convert m/s to mph?
Multiply by 2.236936: 10 m/s is 22.36936 mph. The short route is m/s × 3.6 to get km/h, then ÷ 1.609344 to get mph, which is the same chain this converter runs.
Is 1 ft/s exactly 0.3048 m/s?
Yes. The foot is defined as exactly 0.3048 m, so feet per second convert to meters per second without any rounding. The old road-design figure of 88 ft/s, used to check stopping distances, is exactly 60 mph.
Why is Mach not a unit option?
Because Mach is a multiple of the local speed of sound, and sound travels at about 343 m/s at 20 °C near sea level but about 295 m/s at 36,000 ft. There is no single factor, so a Mach conversion needs an altitude and temperature to go with it.