Speed Converter: Units, Formulas, and Examples
Convert speeds between km/h, mph, meters per second, knots, and feet per second.
How to convert speed
Converted value = input value × source factor ÷ target factor. Factors express each unit in meters per second.
Keep the source and target definitions consistent, apply the conversion to the original value, and round the final answer to the precision needed for your calculation.
Understanding speed units
Speed expresses distance traveled per time interval. One knot is one nautical mile per hour. One nautical mile is exactly 1,852 meters.
| Unit | In m/s |
|---|---|
| Meters per second (m/s) | 1 |
| Kilometers per hour (km/h) | 0.277777777778 |
| Miles per hour (mph) | 0.44704 |
| Knots (kn) | 0.514444444444 |
| Feet per second (ft/s) | 0.3048 |
| Centimeters per second (cm/s) | 0.01 |
Worked speed examples
100 km/h is approximately 62.1371192237 mph. 1 m/s = 3.6 km/h; 60 mph = 96.56064 km/h.
Frequently asked questions
Which definitions should I use?
Mach depends on the speed of sound in the surrounding medium and its conditions. A fixed Mach factor would be misleading, so it is not included.
Why do displayed results sometimes differ slightly?
Intermediate arithmetic uses browser floating-point numbers. Display rounding and the precision of an original measurement can affect the last digits. The unit conversion does not improve the accuracy of a measured value.
Does converting back recover the original value?
Using the unrounded result normally recovers the original quantity within floating-point precision. Copying a rounded number can introduce a small difference.
How are the unit definitions documented?
For physical unit definitions and conversion factors, see the NIST conversion reference.