Race Time Predictor
Enter a known race result and predict your finish time at any distance using the Riegel formula.
How is this calculated?
This calculator uses the Riegel formula, the most widely used race time prediction model:
T2 = T1 × (D2 / D1)1.06
Where T1 is your known time, D1 is the known distance, and D2 is the target distance. The exponent 1.06 accounts for the natural slowing that occurs as race distance increases.
Predictions are most accurate when the known race distance is reasonably close to the target. Extrapolating from a 5K to a marathon, for example, may be less accurate than from a half marathon.