Units of speed
A speed is a distance divided by a time, so every speed unit pairs a length unit with a time unit. The meter per second is the scientific unit. Kilometers per hour fill road signs in most countries, while the United States and the United Kingdom post limits in miles per hour. At sea and in the air, speeds are given in knots, one nautical mile per hour, and engineers in the US sometimes use feet per second.
How to use this converter
Type a speed in any field and the other units update as you type. Each common pair below the converter has its own page with the formula, a worked example and a chart, handy when driving abroad or reading a marine forecast.
Exact factors
All the factors are exact because they come from exact definitions of the mile, the foot and the nautical mile:
- 1 mph = 1.609344 km/h = 0.44704 m/s
- 1 knot = 1.852 km/h ≈ 1.15078 mph
- 1 m/s = 3.6 km/h ≈ 2.23694 mph
- 1 ft/s = 1.09728 km/h ≈ 0.681818 mph
Speed, time and distance
Speed links distance and time: distance = speed × time. At 60 mph you cover one mile per minute, and at 90 km/h you cover 1.5 km per minute. For running, the inverse of speed, called pace, is more common: 10 km/h corresponds to a pace of 6 minutes per kilometer, and 6 mph to 10 minutes per mile.
Tips
When converting a speed limit, round down rather than up to stay on the safe side. For wind, check the unit carefully: forecasts may use km/h, mph, m/s or knots depending on the country and the audience, and the same number can mean very different winds.
Speed units compared
| Unit | Symbol | In meters per second |
|---|---|---|
| Meter per second | m/s | 1 |
| Kilometer per hour | km/h | 0.277778 |
| Mile per hour | mph | 0.44704 |
| Knot | kn | 0.514444 |
| Foot per second | ft/s | 0.3048 |
The units in detail
What is a meter per second?
The meter per second is the SI unit of speed. Physicists, engineers and many weather services use it, especially for wind. A world-class sprinter averages a little over 10 m/s over 100 m, and 1 m/s equals 3.6 km/h or about 2.24 mph.
What is a kilometer per hour?
The kilometer per hour is the speed unit on road signs and speedometers in most of the world, including Canada and Mexico. A highway limit of 100 km/h is about 62 mph, and 50 km/h, a common city limit, is about 31 mph.
What is a mile per hour?
The mile per hour is the unit of speed limits in the United States and the United Kingdom. Since a mile is exactly 1.609344 km, 1 mph is exactly 1.609344 km/h. Baseball pitches, wind speeds in US forecasts and treadmill displays also use mph.
What is a knot?
The knot is one nautical mile per hour, exactly 1.852 km/h or about 1.15 mph. Ships, aircraft and marine weather forecasts use it worldwide. The name comes from sailors counting knots on a line paid out behind the ship.
What is a foot per second?
The foot per second is exactly 0.3048 m/s, or about 0.68 mph. It appears in US engineering, fluid flow, ballistics (muzzle velocity) and physics homework that uses customary units.