Race Time Predictor
Predict your 5K, 10K, half marathon and marathon times from any recent race result, using Riegel's endurance formula — with the target paces to match.
Use a race or hard time trial from the last few weeks, not a training run.
How this is worked out
Predictions use Riegel’s endurance formula: your predicted time equals your known time multiplied by the ratio of the two distances raised to the power 1.06. That exponent is the standard road-running value and encodes how pace decays as distance grows.
The model assumes you are equally trained for both distances. It is reliable within about 3× of your input and optimistic beyond that — a fast 5K does not by itself make you a marathoner. Rows more than 3× away are marked.
Information only — not medical advice. These are estimates from population-level formulas, not a substitute for professional assessment. See our full disclaimer.
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