Running Pace Calculator and Race Time Predictor
Work out your pace per kilometre and per mile from a distance and time, and predict your 5K, 10K, half marathon and marathon times. Free, private and instant.
How to use the Running Pace Calculator and Race Time Predictor
- Choose the distance you ran, or Custom distance and its unit.
- Enter your finish time in hours, minutes and seconds.
- Read your pace per kilometre and mile and your speed.
- Use the prediction table to see what the same effort could mean at 5K, 10K, half marathon and marathon distances.
Example
Worked example (5K in 25:00)
- Pace: 5:00 per km, 8:03 per mile
- Speed: 12.00 km/h (7.46 mph)
- Predicted 10K: 52:07
- Predicted half marathon: 1:55:00
- Predicted marathon: 3:59:47
Limitations
- Riegel is an estimate. It assumes you are trained for the longer distance, so it can be optimistic for the marathon.
- Hills, heat, wind and pacing change real race times.
- Pace is shown to the nearest second.
- This is not linked to any fitness app or watch.
Sources
Rates and rules last checked against these sources on 2026-10-08.
About this tool
The Running Pace Calculator turns a distance and time into your pace per kilometre and per mile and your speed in km/h and mph, then predicts your finish times at other distances using the Riegel formula, which says time grows with distance to the power of 1.06. It is a good guide when your training is consistent, but longer races need more endurance than the formula assumes, so treat the marathon figure as a best case.
Also searched for as: pace calculator, running pace per km and per mile, race time predictor, 5k to 10k time prediction, marathon time predictor, riegel formula calculator, min per mile to km.
Running Pace Calculator and Race Time Predictor is part of ToolStack Hub's Calculators. It runs entirely in your browser, which keeps your data private and makes results instant. There is nothing to install and no account to create. There is no usage limit.
Frequently asked questions
How do I calculate running pace?
Divide your total time by the distance. A 25-minute 5K is 25 ÷ 5 = 5 minutes per kilometre.
How do I convert min per km to min per mile?
Multiply by 1.609344. 5:00 per km is 8:03 per mile.
How accurate is the race predictor?
It is a reasonable guide from 5K to the half marathon if your training suits the distance, and less reliable for the marathon.
Is the Running Pace Calculator and Race Time Predictor free?
Yes. Running Pace Calculator and Race Time Predictor is completely free with no sign-up, limits or watermarks.
Is my data private when I use the Running Pace Calculator and Race Time Predictor?
Yes. It runs in your browser, so your input is not uploaded to our servers.
Does it work on mobile?
Yes. ToolStack Hub tools work on phones, tablets and desktop browsers.
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