Running pace calculator

Divide your total time by the distance. Ten kilometers in 50 minutes is 3000 seconds over 10 kilometers, which is 300 seconds per kilometer, or 5:00 per kilometer.

The part that trips people up is reading the result. Pace is minutes and seconds per kilometer, not a decimal number of minutes: 5.5 minutes per kilometer is 5:30, not 5:50. Writing it the wrong way is the classic mistake, and it slips through because the number still looks right.

With Riegel's formula, published in 1977: predicted time = your time x (new distance / your distance) raised to the power of 1.06.

The exponent is the whole point. If it were 1.0 the prediction would be a straight proportion, and a runner who does 10 km in 50 minutes would be predicted to run the marathon in 3h31. With 1.06 the prediction is 3h50, because nobody holds the same pace over a longer distance.

It is an empirical estimate fitted to real race results, not a promise. It works best between half and double the distance you entered, so predicting a marathon from a 5 km is the least reliable direction.

It also assumes you have trained for the longer distance. The formula describes how pace decays with distance for a runner who can actually cover it; it cannot know whether your longest run so far is 12 kilometers.

They are the same information upside down. Pace is time per distance and gets smaller as you get faster; speed is distance per time and gets bigger.

Runners think in pace because a race is planned in minutes per kilometer, while cycling and treadmills usually show speed in kilometers per hour. This tool shows both so you can move between the two without doing the conversion in your head.