Miles to kilometres
One mile is exactly 1.609344 kilometres. Multiply miles by 1.609344. The same factor converts speeds, so 30 mph is 48.3 km/h, 55 mph is 88.5 km/h and 70 mph is 112.7 km/h, which is why European limits sit at 50, 90 and 110 rather than at tidy conversions.
How to convert miles to kilometres
Adding sixty per cent is the shortcut worth knowing: sixty miles plus sixty per cent gives 96, against a true 96.56. It is accurate to under one per cent all the way up, which is closer than a car speedometer is required to be.
Questions
Yes. Miles per hour and kilometres per hour share the same factor, so the conversion is identical: only the unit label changes.
It descends from the Roman mille passus, a thousand paces, then was fixed at 1,760 yards by an English statute of 1593. The metric value came later, when the yard was tied to the metre.
26.2188 miles is 42.195 km. The distance was set at the 1908 London Olympics and standardised in 1921.
An older US definition, longer by about two parts per million. It was used for land surveying and was officially retired at the end of 2022.