Race Time Predictor
Predict a race finish time at another distance.
From one race to the next
A recent race result predicts your potential at other distances remarkably well. Riegel’s formula scales your time using an endurance exponent, capturing how pace slows as distance grows.
A 50-minute 10K predicts a half marathon of about 1:50. Enter a known race and a target distance, and it estimates the finish time — a great way to set a realistic race goal.
Reliable and private
The calculation runs in your browser, so nothing you enter is uploaded.
Frequently Asked Questions
How does it predict?
Riegel’s formula scales a recent race time to a new distance using an endurance exponent of 1.06.
How accurate is it?
It is a solid estimate for well-trained runners across common distances, but assumes similar conditions and proper training for the new distance.
What do I enter?
A recent race distance and time, plus the target distance you want a prediction for.
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