How this speed converter works
Speed is distance divided by time, and it can be expressed in many units: metres per second (m/s) in science, kilometres per hour (km/h) and miles per hour (mph) on roads, knots at sea and in the air, feet per second (ft/s) in engineering, and Mach for very high speeds. To convert accurately between them, this tool turns whatever you type into a single base unit — metres per second — and then expresses that base value in every other unit. Converting through a base avoids the rounding errors that creep in when you chain conversions one after another.
The exact factors used are: 1 km/h = 0.277778 m/s, 1 mph = 0.44704 m/s, 1 knot = 0.514444 m/s, and 1 ft/s = 0.3048 m/s. Mach is calculated as metres per second divided by 343, assuming the speed of sound at standard sea level (about 343 m/s) — the real speed of sound changes with air temperature and altitude. The most-searched pairing — miles per hour to kilometres per hour — is highlighted at the top so you can read it at a glance.
Common conversions
| From | Equals |
|---|---|
| 1 mile per hour (mph) | 1.609 kilometres per hour (km/h) |
| 60 miles per hour (mph) | 96.56 kilometres per hour (km/h) |
| 100 kilometres per hour (km/h) | 62.14 miles per hour (mph) |
| 10 knots (kn) | 18.52 kilometres per hour (km/h) |
| 1 Mach (sea level) | 1,234.8 kilometres per hour (km/h) |
Reference note: road and air speeds use the international mile (1.609344 km) and nautical mile (1.852 km, exact). Mach assumes 343 m/s at standard sea level. Results are rounded for readability, so very small differences in the last decimal are normal.
Frequently asked questions
- How do I convert mph to km/h?
- Multiply the number of miles per hour by 1.609344 to get kilometres per hour. For example, 1 mph = 1.609 km/h and 60 mph ≈ 96.6 km/h. This converter does it instantly the moment you type a value.
- How fast is 1 knot?
- One knot is one nautical mile per hour, which equals exactly 0.514444 metres per second, about 1.852 km/h or roughly 1.151 mph. Knots are used at sea and in aviation.
- What is Mach 1?
- Mach 1 is the speed of sound. This tool uses the standard sea-level value of about 343 metres per second (roughly 1,235 km/h or 767 mph). The actual speed of sound varies with air temperature and altitude.
- How many m/s in km/h?
- One kilometre per hour equals 0.277778 metres per second (that is 1000 m divided by 3600 s). To go the other way, multiply metres per second by 3.6 to get km/h.
- How do I convert km/h to mph?
- Divide the number of kilometres per hour by 1.609344, or multiply by 0.621371, to get miles per hour. For example, 100 km/h ≈ 62.14 mph.
- What is a knot used for?
- The knot is the standard unit of speed for ships, boats and aircraft, because it ties directly to nautical miles and latitude on charts. One knot is one nautical mile per hour.