Speed converter
Convert between mph, km/h, knots and meters per second in real time. You'll also see the Mach number for your speed, plus practical references to compare against.
Enter a speed to see the conversion instantly.
| Reference (tap to try it) | mph | km/h |
|---|---|---|
| Brisk walk | 4 | 6.4 |
| City cycling | 15 | 24.1 |
| Typical city speed limit | 30 | 48.3 |
| US interstate speed limit | 70 | 112.7 |
| Airliner at cruise | 559 | 900 |
| Speed of sound (air, 68 °F) | 767.3 | 1,234.8 |
Conversion factors between mph, km/h, knots and m/s
A statute mile is 1,609.344 meters, so 1 mph equals 1.609 km/h — a quick rule of thumb is to add about 60% to mph to get km/h, or take roughly 60% of km/h to get mph. The meter per second is the SI unit: 1 m/s is exactly 3.6 km/h, or about 2.24 mph. The knot, used at sea and in aviation, is one nautical mile per hour (1.852 km/h, about 1.15 mph); the nautical mile was originally defined as one minute of arc along a meridian of the Earth.
Speed limits and other useful reference points
In the US, interstates typically allow 65–75 mph depending on the state, while most European highways sit around 120–130 km/h — so a rental-car speedometer showing 130 km/h means roughly 81 mph. The speed of sound in air at 68 °F (20 °C) is about 343 m/s, i.e. 767 mph or 1,235 km/h: that's the famous Mach 1, and the tool automatically shows what fraction of Mach your value corresponds to.