Race Time Predictor
Enter a recent race result and get projected finish times for the 5K, 10K, half marathon and marathon.
Predicted times
| Race | Predicted time | Pace / km |
|---|---|---|
| 5K | 23:59 | 4:48 |
| 10K | 50:00 | 5:00 |
| Half Marathon | 1:50:19 | 5:14 |
| Marathon | 3:50:01 | 5:27 |
Based on Riegel's formula. Predictions assume similar training and course conditions.
How the prediction works
This tool uses Peter Riegel's endurance formula: T2 = T1 × (D2 / D1)^1.06. The 1.06 exponent accounts for the fact that we slow down slightly as distance increases. It's widely used because it's accurate for runners with consistent endurance training.
Tips for accurate predictions
Use a recent, all-out race effort for the input. Marathon predictions from a 5K tend to be optimistic unless you've done the long-run mileage — treat the marathon row as a best-case target.