Enter a recent race result and predict your time at other distances using the Riegel formula.
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| Distance | Predicted time | Pace (min/km) | Pace (min/mi) |
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Based on Pete Riegel's formula: t₂ = t₁ × (d₂ ÷ d₁)^1.06. Predictions become less accurate for large changes in distance.
How does the Race Time Estimator work?
It uses Pete Riegel's formula (1977): t₂ = t₁ × (d₂ ÷ d₁)^1.06
where t₁ is your known time, d₁ is the known distance, d₂ is the target distance, and t₂ is the predicted time. The exponent 1.06 reflects the typical fatigue factor in endurance running.
Limitations
- Most accurate when predicting within ±1–2 distance tiers (e.g. 10K → HM).
- Marathon predictions from a 5K are less reliable — marathon is as much about fuelling as fitness.
- Assumes similar race conditions (flat course, good weather, good preparation).