How to use the pace calculator
Enter the distance you ran, walked or cycled and the time it took. The calculator shows your average pace per kilometer and per mile, your speed in km/h and mph, and your pace for a 400-meter track lap – handy for interval training. A table then predicts what you could run over other popular race distances, both at exactly the same pace and with a fatigue-adjusted prediction.
Pace versus speed
Runners usually talk about pace – the time it takes to cover one unit of distance, such as 5:30 per kilometer. Cyclists and drivers think in speed – distance per hour. They are simply inverses of each other:
How race predictions work
Nobody can hold their 5K pace for a full marathon, so the "Riegel prediction" column uses the formula published by engineer Peter Riegel in 1977:
The exponent 1.06 reflects the gradual slowdown over longer distances. Predictions are most reliable when the two distances are fairly close and when you have trained properly for the longer event – a 10K result predicts a half marathon better than a 1-mile time predicts a marathon.
Training with pace
- Easy runs: roughly 60–90 seconds per km slower than your 10K race pace. Most of your weekly mileage should be easy.
- Tempo runs: about the pace you could hold for one hour – comfortably hard.
- Intervals: near 5K pace or faster, with recovery jogs in between; use the lap pace to hit your target on a track.
- Race day: start a little slower than goal pace and finish strong.
Heat, hills, wind and altitude all slow you down, so adjust targets on tough days.
Worked example
If you finish a 10 km run in 50 minutes, your pace is 5:00 per kilometer, or about 8:03 per mile, and your average speed is 12 km/h. The Riegel formula predicts a half marathon time of roughly 1:51 and a marathon of around 3:51, assuming suitable endurance training.
Frequently asked questions
How do I calculate my running pace?
Divide your total time by the distance. For example, 50 minutes for 10 km is a pace of 5:00 per kilometer.
How do I convert pace per km to pace per mile?
Multiply the pace per kilometer by 1.609. A 5:00/km pace is about 8:03 per mile.
How accurate are race time predictions?
They are reasonable estimates for trained runners, but actual results depend on training, course and conditions. Longer extrapolations are less accurate.
What is a good 5K time?
It varies by age and experience. Many recreational runners finish between 25 and 35 minutes; under 20 minutes is considered fast for amateurs.
Last reviewed 2026-10-27. This pace calculator is provided for general information; verify important decisions with a qualified professional.