Running pace calculator
Fill in two of distance, time and pace to get the third, in minutes per kilometre or per mile — then see splits and predicted times for other race distances.
Splits
Race predictions Riegel
Runs entirely in your browser. Nothing you enter is sent to a server.
Pace, time and distance
pace = time ÷ distance. A 10 km run in 52:30 is 5:15 per km (8:27 per mile). Speed is the inverse: 60 ÷ 5.25 = 11.4 km/h.
Race predictions
Predictions use Peter Riegel’s formula, T₂ = T₁ × (D₂ ÷ D₁)1.06. It works best between similar distances and assumes you’ve trained for the longer race — marathon predictions from a 5K are often optimistic.
Common goal paces
| Sub-25 min 5K | 4:59/km |
| Sub-50 min 10K | 4:59/km |
| Sub-2 hour half | 5:41/km |
| Sub-4 hour marathon | 5:41/km |
Train by effort with the heart rate zone calculator, and time intervals with the stopwatch.
Frequently asked questions
What pace is a 4-hour marathon?
5:41 per km, or 9:09 per mile.
How do I type times?
Use colons: 52:30 for 52 minutes 30 seconds, or 1:45:00 for 1 hour 45 minutes.
How accurate are race predictions?
Good for nearby distances. For the marathon, add a few minutes unless you’ve done long training runs.