How to convert speed
- km/h to mph: divide by 1.609344 (100 km/h = 62.14 mph).
- mph to km/h: multiply by 1.609344.
- m/s to km/h: multiply by 3.6 (10 m/s = 36 km/h).
- Knots to km/h: multiply by 1.852. A knot is one nautical mile per hour.
The speed of sound changes with temperature. Mach 1 here is 340.29 m/s (1,225 km/h), the value for sea level at 15 °C. At airliner cruising altitude it is about 295 m/s.
Common speed conversion factors
| Unit | Equals | Reverse |
|---|---|---|
| 1 kilometre per hour | 0.6213711922 mph | 1 mile per hour = 1.609344 km/h |
| 1 metre per second | 3.6 km/h | 1 kilometre per hour = 0.2777777778 m/s |
| 1 knot | 1.852 km/h | 1 kilometre per hour = 0.5399568035 kn |
| 1 foot per second | 0.3048 m/s | 1 metre per second = 3.280839895 ft/s |
| 1 Mach (sea level, 15 °C) | 1,225.044 km/h | 1 kilometre per hour = 0.0008162972 Ma |
| 1 mile per hour | 0.44704 m/s | 1 metre per second = 2.236936292 mph |
| 1 knot | 1.150779448 mph | 1 mile per hour = 0.8689762419 kn |
Speed conversions
Each of these has its own page with the formula, worked examples and a full conversion table:
Kilometres per hour to miles per hourMiles per hour to kilometres per hourMetres per second to kilometres per hourKilometres per hour to metres per secondKnots to kilometres per hourKilometres per hour to knotsKnots to miles per hourMiles per hour to knotsMach (sea level, 15 °C) to kilometres per hourFeet per second to metres per second
All speed units on this converter
| Unit | Symbol | 1 unit equals | System |
|---|---|---|---|
| Millimetre per second | mm/s | 0.001 m/s | Metric |
| Centimetre per second | cm/s | 0.01 m/s | Metric |
| Metre per second | m/s | 1 m/s | Metric |
| Kilometre per hour | km/h | 0.2777777778 m/s | Metric |
| Kilometre per second | km/s | 1,000 m/s | Metric |
| Mile per hour | mph | 0.44704 m/s | Imperial / US |
| Foot per second | ft/s | 0.3048 m/s | Imperial / US |
| Foot per minute | ft/min | 0.00508 m/s | Imperial / US |
| Knot | kn | 0.5144444444 m/s | Navigation & science |
| Mach (sea level, 15 °C) | Ma | 340.29 m/s | Navigation & science |
| Speed of light | c | 29,97,92,458 m/s | Navigation & science |
Frequently asked questions
How do I convert km/h to mph?
Divide by 1.609344. For example 80 km/h ÷ 1.609344 = 49.7 mph.
How fast is Mach 1?
About 1,225 km/h (761 mph) at sea level and 15 °C; it is slower at high altitude where the air is colder.
What is a knot?
One nautical mile per hour: 1.852 km/h or 1.15078 mph. It is used for ships, aircraft and wind speed.