To convert from miles per hour to kilometers per hour:
Take your speed.
Multiply the value by 1.6.
To convert kilometers per hour to miles per hour:
Take your speed.
Multiply the value by 0.62.
A handy trick if you don’t have a calculator to hand (e.g., you're driving) is to use the Fibonacci sequence (1, 1, 2, 3, 5, 8…). Take a number; the next one in the sequence is the kilometers if the previous one was miles (e.g., 50 mph is roughly 80 kph). Read more