Kilometres per hour to miles per hour
Convert km/h to mph. Multiply by 0.621371, with speed limit tables for driving abroad and a table of common driving speeds.
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The formula
mph = km/h × 0.6213711922It is the same factor as for distance, because a speed is a distance divided by a time and the time unit is the hour on both sides. See km to miles.
To go the other way, multiply by 1.609344. See mph to km/h.
Quick reference
| km/h | mph |
|---|---|
| 10 km/h | 6.2 mph |
| 30 km/h | 18.6 mph |
| 50 km/h | 31.1 mph |
| 80 km/h | 49.7 mph |
| 100 km/h | 62.1 mph |
| 120 km/h | 74.6 mph |
| 130 km/h | 80.8 mph |
| 200 km/h | 124.3 mph |
Speed limits
The numbers are round in whichever system the country legislates in, and awkward in the other. This is the table for driving abroad:
| Metric country | Limit | In mph |
|---|---|---|
| Urban | 50 km/h | 31.1 mph |
| Residential / school zone | 30 km/h | 18.6 mph |
| Rural single carriageway | 80–90 km/h | 49.7–55.9 mph |
| Expressway | 100 km/h | 62.1 mph |
| Motorway | 110–130 km/h | 68.4–80.8 mph |
| mph country | Limit | In km/h |
|---|---|---|
| UK built-up area | 30 mph | 48.3 km/h |
| UK single carriageway | 60 mph | 96.6 km/h |
| UK motorway | 70 mph | 112.7 km/h |
| US urban | 25–35 mph | 40.2–56.3 km/h |
| US interstate | 65–75 mph | 104.6–120.7 km/h |
Two numbers worth committing to memory: 100 km/h is 62 mph, and 60 mph is 97 km/h.
Cars sold in both markets
A speedometer marked in both scales usually puts km/h on the inner ring. The gap between the two readings widens with speed, which is why a car cruising at “70” means something very different on a British motorway than on a German autobahn.
| Speedometer reading | If km/h | If mph |
|---|---|---|
| 30 | 18.6 mph | 48.3 km/h |
| 50 | 31.1 mph | 80.5 km/h |
| 70 | 43.5 mph | 112.7 km/h |
| 100 | 62.1 mph | 160.9 km/h |
Estimating in your head
Halve it and add 20% of the half. 100 km/h halves to 50, plus 10 is 60 mph against a true 62.1. The Fibonacci trick works for speed exactly as it does for distance, since the factor is the same: 80 km/h decomposes as 55 + 21 + 3 + 1, giving 34 + 13 + 2 + 1 = 50 mph against a true 49.7.