Race Time Predictor
Enter a recent race result and we'll predict your finish times across every standard distance, using Pete Riegel's endurance formula. Best with a result from the last few weeks.
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Your predicted times
| Distance | Predicted time | Pace / km |
|---|---|---|
| 5K | 25:00 | 5:00/km |
| 10K | 52:07 | 5:13/km |
| Half Marathon | 1:55:00 | 5:27/km |
| Marathon | 3:59:47 | 5:41/km |
Sources & method
Uses the Riegel formula: T₂ = T₁ × (D₂ / D₁)¹·⁰⁶, from Pete Riegel, "Athletic Records and Human Endurance" (American Scientist, 1981). The 1.06 fatigue factor is the widely-used endurance constant.
Predictions assume comparable conditions and appropriate training for the longer distance — treat marathon predictions from a 5K as optimistic without the mileage to back them up.