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Race Time Predictor
Enter a recent race and a target distance to estimate your finish time, using the Riegel formula.
hh:mm:ss or mm:ss
Predicted time—
Pace · per km—
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How it's calculated
It uses Pete Riegel's endurance formula: predicted time equals your known time multiplied by the distance ratio raised to the power 1.06. The exponent captures how pace slows as distance grows. It is most accurate for nearby distances; big jumps such as 5K to marathon tend to be optimistic because they ignore your specific endurance and fuelling.
FAQ
How accurate is it?
Good for similar distances, rough for large extrapolations. Pair it with the VDOT calculator and your own long-run experience.