MPH to KMH converter

MPH to KMH: multiply by 1.609344

One mile per hour equals exactly 1.609344 kilometers per hour. Multiply an mph value by that factor to get km/h. For the reverse conversion, divide the km/h value by 1.609344. The tool displays up to two decimal places.

For example, 60 mph converts to 96.56064 km/h, displayed here as 96.56 km/h. Starting with 100 km/h gives approximately 62.14 mph. The numerical result changes because a mile is longer than a kilometer; the physical speed stays the same.

The labels kmh, kph and km/h are commonly used for kilometers per hour. This page uses km/h in results and tables. Select the direction before calculating so a number copied from a dashboard or a trip record is interpreted in its original unit.

Common mph to km/h conversions

Use this chart for a quick reference, then enter a specific value in the converter when you need another speed. These are unit conversions, not recommended speeds or local road limits.

Multiplying mph by 1.6 is a useful rough estimate. It puts 50 mph at about 80 km/h, compared with the exact conversion of 80.4672 km/h. Use the full factor when preparing a table or comparing exported numbers, especially when several conversions build on one another.

Round the answer, keep the original measurement

Round after conversion when you can. Rounding both the original number and the result can hide small differences between records. A value displayed as 60 mph may already have been rounded by the device that produced it.

More decimal places do not make a GPS measurement more accurate. The conversion factor is exact, but the speed entered may contain sensor uncertainty, display rounding or filtering. Keep those separate when checking whether two speed displays agree.

If two records use different units, convert one of them before comparing. If they still disagree, look at the same moment in the journey and check whether each value is instantaneous, average or maximum speed. Unit conversion alone cannot turn an average into a live reading.

For a table of whole-number speeds, choose a consistent rounding rule and label the column. Mixing mph and km/h without visible units makes a normal change of scale look like a sudden change in pace.

Where the conversion factor comes from

NIST's Guide for the Use of the International System of Units lists the international mile as 1,609.344 meters. Dividing by 1,000 gives the kilometer factor used here. Both speed units use the same hour, so no further time conversion is needed.

• NIST Special Publication 811: unit conversion factors