Running Pace Calculator
Calculate running pace per kilometer and per mile, speed, and projected 5K, 10K, half and full marathon times.
Pace vs speed
Runners usually talk about pace, the time it takes to cover one kilometer or one mile, rather than speed. Pace is simply finish time divided by distance.
Pace = Time ÷ Distance Speed = Distance ÷ Time
Running 10 km in 52:30 gives a pace of 5:15 per km (8:27 per mile), a speed of 11.4 km/h.
Predicting race times
The calculator projects your times at other distances with Peter Riegel's formula, published in 1977:
T2 = T1 × (D2 ÷ D1)^1.06
The exponent 1.06 reflects the fact that runners slow down as distance increases. Predictions are most reliable between similar distances, for example from a 10K to a half marathon. Marathon predictions from short races are often optimistic unless your weekly mileage is high.
Using pace in training
- Easy runs: about 60–90 seconds per km slower than your 10K pace.
- Tempo runs: roughly the pace you could hold for an hour.
- Intervals: around 5K pace or faster, with recovery between repeats.
Use the heart rate zone calculator alongside pace on hilly or hot days, when effort matters more than the clock.
Frequently asked questions
What is a good 5K time?
For recreational runners, finishing a 5K in 25–35 minutes is common. Under 20 minutes is a strong time for most age groups.
How do I convert pace per km to pace per mile?
Multiply the pace per km by 1.609. For example, 5:00 per km is about 8:03 per mile.
How accurate are race time predictions?
They are a reasonable guide when you are trained for the target distance. They tend to be optimistic for the marathon if your training volume is low.
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.