The conversion factor
1 kilometers per hour equals 0.621372 miles per hour. Multiply your kilometers per hour value by 0.621372 to get miles per hour; divide to go back. For the reverse direction, use the miles per hour to kilometers per hour converter or the full speed converter.
Where this conversion comes up
Mixing metric and imperial is a daily reality in travel, shipping, recipes, fitness apps, and spec sheets — this page gives the exact factor plus a scannable table for the values people actually need.