Speed Converter
Convert speeds between km/h, mph, m/s, ft/s and knots, with the matching running or cycling pace per kilometer and per mile.
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Updated Formula covered by automated tests
Convert a speed between kilometers per hour, miles per hour, meters per second, feet per second and knots. For walking, running and cycling speeds the converter also shows the matching pace in minutes per kilometer and minutes per mile, the figure most training plans and running watches actually use.
Different groups settled on different speed units for practical reasons. Road signs use km/h or mph because drivers think in hours of travel; physicists and wind engineers use m/s because it plugs straight into SI equations; ships and aircraft use knots because charts measure distance in nautical miles. If you drive abroad, read a weather report with wind in m/s, or compare a treadmill set in mph with a race plan in min/km, you need to cross between them.
The formula
- m/s
- Meters per second, the SI unit of speed that the converter uses internally
- 3.6
- Seconds in an hour (3600) divided by meters in a kilometer (1000)
- kn
- Knot: one nautical mile (exactly 1852 m) per hour
- pace
- Time to cover a fixed distance; the reciprocal of speed, so doubling speed halves pace
Each speed unit is a distance unit divided by a time unit, so its m/s value follows directly from exact length definitions. A mile is 1609.344 m and an hour 3600 s, so 1 mph is 1609.344 ÷ 3600 = 0.44704 m/s exactly. The knot comes from the nautical mile, which was originally one minute of latitude and was fixed at 1852 m by international agreement in 1929.
Pace is the reciprocal of speed, which is why it does not scale the way people expect. Going from 10 to 12 km/h improves pace from 6:00 to 5:00 per km, but going from 12 to 14 km/h only improves it to 4:17. The pace line in the converter is computed from the same m/s value, rounded to the nearest second.
Worked example
Lena runs comfortably at 10 km/h on her gym treadmill in Berlin. Her new American training plan prescribes runs in minutes per mile and lists treadmill speeds in mph.
- 1 Convert to meters per second: 10 ÷ 3.6 = 2.7778 m/s.
- 2 Convert to mph: 2.7778 ÷ 0.44704 = 6.2137 mph.
- 3 Pace per kilometer: 1000 ÷ 2.7778 = 360 s, which is 6:00 per km.
- 4 Pace per mile: 1609.344 ÷ 2.7778 = 579.4 s, which rounds to 579 s or 9:39 per mile.
Result: Lena’s easy pace is 6.2 mph on a US treadmill, or 9:39 per mile, matching 6:00 per kilometer.
Before you rely on the result
- Converts constant speeds only; it does not average speeds over legs of different lengths, which requires total distance divided by total time.
- Pace is shown only between roughly 1 and 120 minutes per kilometer, the range relevant for walking, running and cycling.
- Mach number is not offered because the speed of sound changes with air temperature and altitude.
Frequently asked questions
Why do pilots and sailors still use knots?
Nautical charts are drawn with latitude and longitude, and one nautical mile is very close to one minute of latitude anywhere on Earth. Measuring speed in nautical miles per hour lets a navigator turn time and speed directly into chart distance without a conversion step. Wind speeds in aviation weather reports are also given in knots.
What is a quick mental conversion between mph and km/h?
Multiply mph by 1.6 for km/h, or multiply km/h by 0.6 (or by 5 and divide by 8) for mph. 50 mph is about 80 km/h and 100 km/h is about 62 mph. The exact factor is 1.609344, so the 1.6 and 5/8 shortcuts are within 1 percent, while 0.6 reads about 3 percent low.
How do I read wind speed given in meters per second?
Many European and Asian forecasts use m/s. Multiply by 3.6 for km/h or by about 2.24 for mph: a 10 m/s wind is 36 km/h or 22.4 mph, a fresh breeze on the Beaufort scale, enough to sway small trees.
Does a speedometer reading convert exactly?
The unit conversion is exact, but the speedometer is not. Regulations in many countries allow a car speedometer to read high but never low, so a dial showing 100 km/h usually means a true speed a few km/h lower. A GPS app usually gives a closer figure on a straight, level road.