Kilometers per Hour to Miles per Hour Converter

About the km/h to mph calculation

One kilometer per hour is exactly 0.621371 miles per hour, so converting between them is a single multiplication. Enter any value above and the result updates as you type. The speed-limit unit across most of the world. Speed limits and vehicle speedometers in the US and UK. Exactly 1.609344 km/h.

Formula

mph = km/h × 0.621371

1 km/h = 0.621371 mph
1 mph = 1.6093 km/h

Worked example

To convert 100 km/h, multiply by 0.621371: 100 × 0.621371 = 62.1371 mph.

Frequently asked questions

How many miles per hour are in a kilometer per hour?

There are 0.621371 miles per hour in one kilometer per hour. To convert any amount, multiply the number of kilometers per hour by 0.621371.

How do I convert miles per hour back to kilometers per hour?

Divide instead of multiplying, or equivalently multiply by 1.6093. One mile per hour is 1.6093 kilometers per hour.

Is this conversion exact?

Yes. Since the international agreement of 1959, the relationship between kilometers per hour and miles per hour is defined exactly rather than measured, so the only rounding here is in how many decimal places we show.

Where is each of these units used?

Kilometers per Hour: the speed-limit unit across most of the world. Miles per Hour: speed limits and vehicle speedometers in the US and UK. Exactly 1.609344 km/h.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units