Race Time Predictor
Predict your finish time for any race distance based on a recent race result.
Uses the Riegel formula — the gold standard for running time prediction.
Predicted Finish Time
Riegel Formula (1977)
T2 = T1 × (D2 ÷ D1)^1.06
Where:
- T1 = finish time for the known race
- D1 = distance of the known race
- D2 = distance of the target race
- T2 = predicted time for the target race
The exponent 1.06 accounts for the fact that longer races require slower paces — you fatigue more over greater distances.
Important: This formula assumes consistent fitness and training. Predictions are most accurate within adjacent distances (e.g., 5K → 10K, 10K → half marathon). Very long extrapolations (5K → marathon) may underestimate finish time.