Convert one 10K time into 5K, half marathon and marathon equivalents
The 10K is the most raced distance and tends to produce a stable time, which makes it a good anchor for estimating everything else. Enter minutes and seconds and you get pace per mile and per kilometre, average speed, the lap time for a 400 m track at that same pace, and a table of 5K, half marathon and marathon equivalents with the pace each needs. No runner level or grade is assigned.
The conversion uses the Riegel distance formula, multiplying your time by the ratio of the two distances raised to the power 1.06, with the original exponent left as it is. The half marathon is taken as 21.0975 km and the marathon as 42.195 km, and miles are converted at 1,609.344 metres (as of October 2026).
Do not take the marathon row at face value. In published studies the formula tracked measured times well up to the half marathon, but predicting a marathon from a shorter race came out at least 10 minutes too fast for half of runners. Marathons are decided by fuelling, heat and the late-race slowdown, and none of that is in the formula. The 5K and half marathon rows are much more dependable, and accuracy drops below about three and a half minutes and above about four hours.
Frequently asked questions
Not safely. In published race-result studies, predicting a marathon from a shorter race came out at least 10 minutes too fast for half of runners. The half marathon row holds up much better.
It applies your average 10K pace to one 400 m lap. It is not an interval prescription, just what one lap costs at that same steady speed.
There is no recognised grading table for 10K times. Tables that circulate disagree with each other, so this page sticks to distance conversion and pace.