Speed Distance Time Calculator
Know two of speed, distance and time? Solve for the third, in any units.
One formula, three questions
distance = speed × time
Rearrange for whichever piece is missing: speed = distance / time, time = distance / speed. 150 km in 2 hours 15 minutes is 150 / 2.25 = 66.7 km/h. The only rule is unit consistency: kilometers with km/h, miles with mph.
The average speed trap
Driving somewhere at 60 and back at 40 does NOT average to 50. Average speed is total distance over total time, which works out to 48 here: the slow leg takes longer, so it drags the average down harder. This (the harmonic mean) is a favorite exam trick.