The conversion factor
1 mile equals 1.609344 kilometers. Multiply your miles value by 1.609344 to get kilometers; divide to go back. For the reverse direction, use the kilometers to miles converter or the full length 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.