Race Predictor Calculator

It uses the Riegel formula: T2 = T1 x (D2/D1)^1.06. This formula assumes that as race distance increases, your average pace slows by a predictable factor (the 1.06 exponent). It works best for trained runners.

For well-trained runners racing between 5K and marathon, predictions are typically within 2-5% of actual results. Less trained runners may see larger discrepancies, especially when predicting longer distances from short race times.

Yes, the formula works in both directions. However, predicting shorter races from longer ones may be less accurate since shorter races depend more on speed than endurance.