Convert Kilometers per Hour to Miles per Hour
Kilometers per hour to miles per hour is the conversion you need whenever a speed is posted in metric but you think in miles — a foreign speed limit sign, a car's specs sheet, a weather report. The number always gets smaller when you switch from km/h to mph, since a mile is longer than a kilometer.
Kilometers per hour to Miles per hour conversion table
| Kilometers per hour (km/h) | Miles per hour (mph) |
|---|---|
| 1 | 0.621371 |
| 2 | 1.242742 |
| 3 | 1.864114 |
| 5 | 3.106856 |
| 10 | 6.213712 |
| 20 | 12.427424 |
| 50 | 31.06856 |
| 100 | 62.137119 |
| 500 | 310.685596 |
| 1,000 | 621.371192 |
The formula
To convert kilometers per hour to miles per hour, multiply the speed in km/h by 0.621371:
mph = km/h × 0.621371
A worked example
Say a car's speedometer reads 100 km/h and you want to know the speed in mph:
100 × 0.621371 = 62.14 mph
So 100 km/h is a little over 62 mph — close to the 65 mph highway speed limit common in the United States.
Why it's an approximation
Kilometers per hour and miles per hour are both tied to exact definitions of the meter and the mile, but when you divide one by the other, the result is a repeating decimal that never ends cleanly. 0.621371 is that number rounded to six decimal places — precise enough for driving, sports, and weather, but technically a rounded value rather than an exact one.
When you'll use it
Reading speed limit signs abroad, converting a car or bike's top speed from a spec sheet, understanding wind speeds in a foreign weather report, and following international racing or cycling coverage.
Frequently asked questions
How many miles per hour is 100 km/h?
About 62.1 mph. Multiply 100 by 0.621371 to get 62.1371, which rounds to 62.1 mph — a common highway speed in countries that use kilometers.
Is the km/h to mph conversion exact?
No, it's a rounded approximation. The true factor is a repeating decimal, so 0.621371 is the true value rounded to six digits — accurate enough for everyday use, but not perfectly exact.
What's a quick way to estimate km/h to mph in my head?
Multiply by roughly 0.6, or divide by 8 and multiply by 5. 100 km/h is close to 60 mph; 160 km/h is close to 100 mph. For anything precise, use the factor above.