How to use
- Enter a speed, then pick the unit you are converting from and the unit you want to.
- The result appears instantly, and the first table shows the same speed in every unit.
- The arrow button swaps the two units. The last table shows familiar reference speeds — walking, highway driving, the speed of sound — in whichever unit you picked.
Conversion factors
Because the mile, foot and nautical mile are defined exactly in meters, conversions between km/h, mph and knots are exact. Mach is the one exception.
| Unit | In m/s | Notes |
|---|---|---|
| 1 km/h | 1/3.6 ≈ 0.27778 m/s | 1 m/s is exactly 3.6 km/h |
| 1 mph | 0.44704 m/s | = 1.609344 km/h |
| 1 knot (kn) | 1,852/3,600 ≈ 0.51444 m/s | one nautical mile per hour |
| 1 ft/s | 0.3048 m/s | 60 mph = 88 ft/s |
| 1 km/s | 1,000 m/s | used for spacecraft and ballistics |
| Mach 1 | 340.294 m/s ≈ 761.2 mph | ISA standard atmosphere, sea level, 15 °C |
Examples
- 65 mph on a US interstate is 104.6 km/h.
- 100 km/h is about 27.78 m/s — roughly 28 meters every second — or 62.14 mph.
- A ship cruising at 20 knots covers 23.02 mph (37.04 km/h).
- A 100 mph fastball travels at 146.7 ft/s.
Things to keep in mind
- Mach is not a fixed speed. The speed of sound depends on air temperature: about 331 m/s at 0 °C and about 343 m/s at 20 °C. This tool uses 340.294 m/s, the International Standard Atmosphere value at sea level and 15 °C. At cruising altitude the air is colder, so Mach 1 is slower in absolute terms.
- Knots are used at sea and in aviation; weather services often report wind in m/s or mph depending on the country.
- To convert between any kind of unit in one box, type something like “100 km/h to mph” into the unit converter.
FAQ
What is the quickest way to turn km/h into m/s?
Divide by 3.6. There are 3,600 seconds in an hour and 1,000 meters in a kilometer, so 3,600 ÷ 1,000 = 3.6. Multiply by 3.6 to go back.
How fast is one knot?
Exactly 1.852 km/h, or about 1.151 mph — one nautical mile per hour.
How do I estimate mph from km/h in my head?
Multiply km/h by 0.6 (or mph by 1.6 for the other way). The exact factor is 1.609344.