Race Time Predictor
Predict 5K, 10K, half marathon and marathon times from a recent race. The result updates as you type, with the working underneath so you can check it.
Your details
Result
Predicted race times
4 distances
Riegel formula predictions
| Distance | Time | Pace | Pace |
|---|---|---|---|
| 10K | 52:07 | 5:13 /km | 8:23 /mi |
| Half marathon | 1:55:00 | 5:27 /km | 8:46 /mi |
| Marathon | 3:59:47 | 5:41 /km | 9:09 /mi |
| 1 mile | 7:31 | 4:40 /km | 7:31 /mi |
- Riegel's formula assumes similar training for the longer distance. Marathon predictions from a 5K are usually optimistic for runners with little mileage.
Good to know: T₂ = T₁ × (D₂ ÷ D₁)^1.06
About this tool
Formula
T₂ = T₁ × (D₂ ÷ D₁)^1.06
Questions people ask
How accurate is the Riegel formula?
Reasonably accurate for well-trained runners across similar distances, but it is optimistic for the marathon if your weekly mileage is low.
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How we calculate this
We use the standard published formula or definition for this calculation, and we show the working so you can check it.
Spotted a mistake? Tell us and we'll check it. How we check our calculators