How to use this speed converter
- Type the speed in the From box. The page opens with 60.
- Pick its unit in the From menu. It has metric, US and UK, and air, sea and physics units, including knots, Mach and the speed of light.
- Pick the unit you want in the To menu. The To box updates as you type, and typing in the To box converts the other way.
- Press Swap units to flip the menus. The panel below lists the same speed in every unit and adds running pace per mile and per kilometer.
How the conversion works
Every speed is converted to meters per second and then to your target unit: value × (From unit in m/s) ÷ (To unit in m/s). The factors are exact definitions. A mile is 1,609.344 m, so 1 mph = 1,609.344 ÷ 3,600 = 0.44704 m/s. A kilometer per hour is 1 ÷ 3.6 m/s. A knot is one international nautical mile (1,852 m) per hour, which is exactly 1.852 km/h. A foot per second is 0.3048 m/s. Speed of light is 299,792,458 m/s. Mach is the ratio to the speed of sound, which depends on air temperature (NASA Glenn explains the formula), so the tool fixes it at the standard sea level value of 340.294 m/s. The unit factors follow NIST SP 811, Appendix B.8. Pace is the time to cover one mile or one kilometer at that speed.
Worked example: 60 mph in km/h
With the default inputs the tool computes 60 × 0.44704 ÷ (1 ÷ 3.6) and shows 60 mph = 96.56064 km/h, with the reverse line 1 km/h = 0.62137119 mph. The panel below it shows 26.8224 m/s, 88 ft/s and 52.138575 knots, and a pace of 1:00 per mile and 0:37 per kilometer.
Common road speeds
| Speed limit | Converted |
|---|---|
| 25 mph | 40.234 km/h |
| 55 mph | 88.514 km/h |
| 65 mph | 104.61 km/h |
| 70 mph | 112.65 km/h |
| 50 km/h | 31.069 mph |
| 100 km/h | 62.137 mph |
| 120 km/h | 74.565 mph |
Limits and edge cases
A knot already means nautical miles per hour, so "knots per hour" is a mistake. Mach is only exact at sea level in standard air; at 11,000 m the speed of sound is about 295 m/s, so a jet's Mach number does not match the sea level mph shown here. Pace shows "n/a" for zero, negative or extremely slow speeds. Negative speeds are otherwise accepted as direction. You can type 1,250 with a thousands comma or 2,5 with a decimal comma, and a pasted 3e8 becomes plain digits. Values above 1,000,000,000,000,000,000,000,000 are refused.
For distances, use the kilometers to miles converter or the length converter. Training for a race? The marathon pace calculator turns a finish time into splits, and the acceleration converter handles m/s² and g-force.
Frequently asked questions
How do I convert mph to km/h?
Multiply the miles per hour by 1.609344. For example, 60 mph × 1.609344 = 96.56064 km/h. For a quick estimate, multiply by 1.6.
How do I convert knots to mph?
Multiply the knots by 1.1507794. For example, 10 knots = 11.507794 mph. One knot is exactly 1.852 km/h.
Why do pilots and sailors use knots?
A knot is one nautical mile per hour, and a nautical mile (1,852 meters) is close to one minute of latitude. That lets a navigator turn distance on a chart straight into time without converting units.
How fast is Mach 1 in mph?
In still air at sea level and 15 °C, Mach 1 is 340.294 m/s, which is 761.216 mph or 1,225.0584 km/h. It is slower at altitude because the air is colder.
How do I convert mph to minutes per mile?
Divide 60 by the speed in mph. A runner at 6 mph covers a mile in 10:00, and the "Pace per mile" line under the converter works this out for any speed you enter.
Sources: NIST SP 811, Appendix B.8 for velocity units, Appendix B.9 for the knot and mile, and NASA Glenn Research Center for the speed of sound.