Miles per hour to kilometres per hour
Convert mph to km/h. Multiply by 1.609344 for an exact result, with speed limit tables and reference speeds for wind and vehicles.
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The formula
km/h = mph × 1.609344This factor is exact, and it is the same one that converts miles to kilometres — a speed is a distance over a time, and the hour is the same on both sides.
To go the other way, multiply by 0.6213711922. See km/h to mph.
Quick reference
| mph | km/h |
|---|---|
| 10 mph | 16.1 km/h |
| 20 mph | 32.2 km/h |
| 30 mph | 48.3 km/h |
| 40 mph | 64.4 km/h |
| 50 mph | 80.5 km/h |
| 60 mph | 96.6 km/h |
| 70 mph | 112.7 km/h |
| 100 mph | 160.9 km/h |
Speed limits in mph countries
| mph | km/h | |
|---|---|---|
| UK built-up area | 30 mph | 48.3 km/h |
| UK 20 zone | 20 mph | 32.2 km/h |
| UK single carriageway | 60 mph | 96.6 km/h |
| UK dual carriageway and motorway | 70 mph | 112.7 km/h |
| US residential | 25 mph | 40.2 km/h |
| US urban arterial | 45 mph | 72.4 km/h |
| US interstate | 70 mph | 112.7 km/h |
| US interstate (Texas, parts) | 85 mph | 136.8 km/h |
A UK 30 mph limit is not a 50 km/h limit — it is 48.3 km/h. Countries that switched from imperial to metric usually rounded down when they redrew the signs, so the equivalent limit became slightly stricter.
Wind speed
American forecasts give wind in mph, which is the odd one out — aviation uses knots, most of the world uses km/h, and East Asia uses metres per second:
| mph | km/h | knots | m/s | |
|---|---|---|---|---|
| 25 mph | 40.2 | 21.7 | 11.2 | strong breeze |
| 39 mph | 62.8 | 33.9 | 17.4 | tropical storm threshold |
| 74 mph | 119.1 | 64.3 | 33.1 | hurricane, category 1 |
| 96 mph | 154.5 | 83.4 | 42.9 | category 2 |
| 111 mph | 178.6 | 96.5 | 49.6 | category 3 |
| 130 mph | 209.2 | 113.0 | 58.1 | category 4 |
| 157 mph | 252.7 | 136.4 | 70.2 | category 5 |
The Saffir–Simpson categories are defined in mph and knots, which is why their metric equivalents are never round numbers.
Reference speeds
| mph | km/h | |
|---|---|---|
| Marathon world record pace | 13.1 mph | 21.0 km/h |
| Cyclist, flat | 15 mph | 24.1 km/h |
| Peak sprint speed (Usain Bolt) | 27.8 mph | 44.7 km/h |
| High-speed train | 200 mph | 321.9 km/h |
| Airliner cruise | 559 mph | 900 km/h |
| Speed of sound at sea level | 767 mph | 1235 km/h |
Estimating in your head
Add 60%: half the number, plus a tenth of it, added on. 70 mph plus 35 plus 7 is 112 km/h — the true answer is 112.7.