Popular speed conversions
Speed units
Speed is distance travelled per unit of time. The SI unit is the meter per second. Road speeds use km/h or mph, and a knot is one nautical mile per hour.
| Unit | Symbol | In meters per second | Definition |
|---|---|---|---|
| Meter per second | m/s | 1 m/s | The SI unit of speed. One meter per second is 3.6 km/h. |
| Kilometer per hour | km/h | 0.2777777778 m/s | The road speed unit in most of the world. |
| Mile per hour | mph | 0.44704 m/s | Exactly 0.44704 meters per second, the road speed unit in the US and UK. |
| Foot per second | ft/s | 0.3048 m/s | |
| Knot | kn | 0.5144444444 m/s | One nautical mile per hour, about 1.852 km/h. Used at sea and in aviation. |
| Kilometer per second | km/s | 1,000 m/s | |
| Mach | Mach | 340.29 m/s | The speed of sound. This converter uses 340.29 m/s, its value in dry air at 15 °C at sea level; the real figure changes with temperature. |
| Speed of light | c | 299,792,458 m/s | Exactly 299,792,458 meters per second. |
Calculate with speed
The smart calculator does arithmetic across speed units and picks a sensible unit for the answer. Try 100 km / 1.5 h to mph.
Questions and answers
Which speed units can I convert?
All 8: meters per second, kilometers per hour, miles per hour, feet per second, knots, kilometers per second, Mach, times the speed of light.
What is the SI unit of speed?
This converter uses the meter per second (m/s) as its base unit. Speed is distance travelled per unit of time. The SI unit is the meter per second. Road speeds use km/h or mph, and a knot is one nautical mile per hour.
What is a knot?
A knot is one nautical mile per hour: exactly 1.852 km/h, or about 1.151 mph.
How precise are the results?
Factors are the exact legal definitions where one exists (an inch is exactly 2.54 cm, a pound exactly 0.45359237 kg). Results show 10 significant digits by default; the precision menu offers 4 to 15.
Does the speed converter work offline?
Yes. ConvertEasy is a progressive web app: after your first visit it keeps working with no connection, and you can install it to your home screen from the browser menu.