Race Time Predictor

How it works

This calculator uses the Riegel formula, the most widely-used race time prediction model in running. It estimates your performance at longer distances by applying an exponential fatigue factor to your known race result. The formula accounts for the fact that pace naturally slows as distance increases, and you can't hold your 5K pace for a marathon.

For the most accurate predictions, use a recent race result (within the last 2-3 months) from a race where you gave a full effort. Training runs and time trials tend to underpredict.