km/h to mph
Convert kilometers per hour to miles per hour. The ratio is the exact 1.609344 that relates the distance units, because an hour is an hour on both sides.
mph = km/h ÷ 1.609344
NIST SP 811 (2008), Appendix B.8 — mile per hour (mi / h) to kilometer per hour (km / h) = 1.609 344 E+00
Speed conversion inherits its factor from distance: the hour cancels out, so kilometers per hour to miles per hour uses exactly the same 1.609344 that converts the distances themselves. This is the conversion drivers need when a rental car shows the wrong unit, and the one sailors avoid entirely by using knots, which are nautical miles per hour rather than statute ones.
How it is calculated
mph = km/h ÷ 1.609344
Because both scales measure distance over the same unit of time, the time cancels and only the distance factor remains. NIST publishes the same number for the speeds as for the lengths.
Common values
| kilometers per hour | miles per hour |
|---|---|
| 10 | 6.2137119 |
| 30 | 18.641136 |
| 50 | 31.06856 |
| 60 | 37.282272 |
| 80 | 49.709695 |
| 90 | 55.923407 |
| 100 | 62.137119 |
| 110 | 68.350831 |
| 120 | 74.564543 |
| 130 | 80.778255 |
| 140 | 86.991967 |
Questions people ask
- What is a 50 km/h city limit in mph?
- 50 km/h is 31.068560 mph, which is why British and American towns tend to post 30 mph — the two limits are close enough to feel identical behind the wheel.
- Is 100 km/h the same as 60 mph?
- Not quite. 100 km/h is 62.137119 mph, so a car cruising at an indicated 60 mph is doing about 96.6 km/h. The gap is small but it is the difference between keeping up with traffic and holding it up.
- Why do ships and aircraft use knots?
- A knot is one nautical mile per hour, and a nautical mile is 1852 meters — roughly one minute of latitude. That makes navigation arithmetic on a chart far simpler than it would be with statute miles.
Related tools
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Liters to Gallons
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