Running Pace Calculator
Enter a distance and a time to see your pace per kilometre and your speed. You can also work out the time at a given pace or the distance, and estimate your 5K, 10K, half marathon and marathon times.
Predicted times
| Race | Predicted time | Pace |
|---|---|---|
| 5K | — | — |
| 10K | — | — |
| Half marathon | — | — |
| Marathon | — | — |
Estimate with Riegel's formula: it assumes you train for each distance. For the marathon it is often optimistic.
Results are estimates. Solvemis accepts no responsibility for the results obtained or for how they are used. Always double-check the result and talk to a qualified professional before making decisions.
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How it works
How to use it
- Choose what to work out: pace, time or distance.
- Enter the other two. For the distance you can tap 5K, 10K, half marathon or marathon.
- Read the result, your speed and your pace per kilometre.
- See the predicted times for common race distances below.
How it is calculated
Pace = time / distance; time = distance × pace; distance = time / pace; speed = 3600 / pace in seconds per kilometre. One mile is 1.609344 km. Predicted times use Riegel's formula: T2 = T1 × (D2 / D1)^1.06, from the distance and time you entered.
Sources
- An empirical study of race times in recreational endurance runners (Vickers & Vertosick, 2016) — BMC Sports Science, Medicine and Rehabilitation
- NIST Special Publication 811: Guide for the Use of the International System of Units — National Institute of Standards and Technology (NIST)
About this calculator
Pace and speed
Runners talk about pace: how long a kilometre takes you (5:00 /km). Treadmills talk about speed: kilometres per hour. They are the same thing upside down:
| Pace | Speed |
|---|---|
| 4:00 /km | 15 km/h |
| 5:00 /km | 12 km/h |
| 6:00 /km | 10 km/h |
| 7:00 /km | 8.6 km/h |
Predicted times
With a recent race you can estimate your time at other distances. The calculator uses Riegel’s formula (1981): time grows a little faster than distance, with an exponent of 1.06. The highlighted row is the distance you entered; each row’s bar is the pace: longer means slower. Treat it as a guide, not a promise:
- It works best between similar distances: a 10K to a half marathon.
- For the marathon it is often optimistic for runners without enough weekly training (Vickers & Vertosick, 2016).
- It assumes the same fitness, a flat course and a cool day.
Paces for common goals
| Goal | Average pace |
|---|---|
| 10K in 50 min | 5:00 /km |
| Half marathon in 1:45 | 4:59 /km |
| Half marathon in 2 h | 5:41 /km |
| Marathon in 3:30 | 4:59 /km |
| Marathon in 4 h | 5:41 /km |
Your data stays on your phone
Everything is calculated in your browser: nothing is sent or saved.
Frequently asked questions
How do I calculate pace per kilometre?
Divide your time by the distance. 10 km in 50 minutes is 5 minutes per kilometre (5:00 /km), which is 12 km/h. Speed is the inverse: 60 divided by the pace in minutes.
What pace do I need for a 4-hour marathon?
About 5:41 per kilometre on average (42.195 km in 4 hours). Choose “Pace”, tap the marathon and enter 4 hours, or choose “Time” and try paces.
How accurate are the predicted times?
They are estimates. Riegel's formula works well between similar distances (10K to half marathon), but it is often optimistic for the marathon in recreational runners, especially without long runs. Heat, hills and the day itself matter a lot.
Why is a half marathon 21.0975 km?
Because it is exactly half of the marathon, which has measured 42.195 km since the 1908 London Olympics.
Updated 2 October 2026
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