Mph to km/h converter

km/h = mph × 1.609344 and mph = km/h × 0.621371.

A mile is exactly 1.609344 km, so the speed factor is the same. Quick estimate: multiply mph by 1.6, or take km/h, halve it and add a tenth of the original (100 km/h → 50 + 10 = 60 mph; exact: 62.1).

Outside the US and the UK, speed limits and car speedometers are in km/h. Typical European limits are 50 km/h in towns (about 31 mph), 90 to 100 km/h on rural roads (56 to 62 mph) and 120 to 130 km/h on motorways (75 to 81 mph). Always check the local rules; limits vary by country and road.

• m/s is used in science and for wind speed in many weather services: 1 m/s = 2.237 mph = 3.6 km/h.
• Knots are used at sea and in aviation: 1 knot = 1.151 mph = 1.852 km/h.

For distances rather than speeds, use the km to miles converter.

All conversions use the exact definitions (1 mile = 1,609.344 m, 1 nautical mile = 1,852 m), and rounding only happens on screen. Choose up to 8 decimal places.

Car speedometers in the US often show both mph and km/h, with the km/h scale in smaller print. Speedometers are usually calibrated to read slightly high rather than low, so your GPS speed can be a little lower than the dashboard shows. That's normal and has nothing to do with the unit conversion.

When you rent a car abroad, the speedometer will show km/h only. Memorize a few pairs: 50 km/h ≈ 30 mph, 80 km/h ≈ 50 mph, 100 km/h ≈ 62 mph and 120 km/h ≈ 75 mph. For any other speed, type it here and pick the decimal places you want.

US forecasts give wind speed in mph, while many other countries use km/h, m/s or knots. A 20 mph wind is 32 km/h or 8.9 m/s. Hurricane categories on the Saffir-Simpson scale are defined in mph, knots and km/h, so the same storm can be described with very different-looking numbers. The Speed quantity here converts all four units at once, so you can compare forecasts from different sources. The conversion runs entirely in your browser.