Running pace calculator with race time predictions
Enter a distance and a finish time to get your pace per kilometre and mile, your speed, and predicted times for every standard race distance.
Runs entirely in your browser — nothing is uploaded.
Leave hours empty for anything under an hour.
Predictions use Riegel’s formula (T₂ = T₁ × (D₂/D₁)^1.06), which is reasonable between about 1500 m and the marathon. It assumes equivalent training for each distance, so it flatters you at the long end — a marathon prediction from a 5K time is optimistic unless you have actually done the endurance work.
How to use
- Choose your unit or a race. Kilometres or miles, or pick a standard distance to fill it in for you.
- Enter the distance and time. Leave the hours box empty for anything under an hour.
- Read your pace and speed. Per kilometre and per mile, plus km/h and mph.
- Check the predictions. Equivalent times at 1 km through marathon, based on the same fitness level.
Questions
What is a good running pace?
It depends entirely on distance and experience. A common recreational 5K pace is 6:00–7:00 per km; a sub-25-minute 5K (5:00/km) is a solid club-runner benchmark. Comparing yourself to your own previous times is far more useful than to averages.
How are the race predictions calculated?
Riegel’s formula: T₂ = T₁ × (D₂/D₁)^1.06. The 1.06 exponent reflects that you inevitably slow as distance grows. It is well regarded between about 1500 m and the marathon.
Why is my marathon prediction too optimistic?
Because Riegel assumes you are equally well trained for every distance. Predicting a marathon from a 5K time assumes endurance you may not have built. Marathons also introduce fuelling and glycogen limits that shorter races never test.
How do I convert pace to speed?
Speed in km/h is 60 divided by your pace in minutes per km. A 5:00/km pace is 60 ÷ 5 = 12 km/h.