Race Time Predictor

Predict your finish time for any race distance from a recent race result using the Riegel formula.

Known distance (km)

Known time (minutes)

Target distance (km)

Enter your recent race result.

How to use

Enter a recent race distance, time, and your target distance to predict your finish.

How does the Riegel formula work?

T2 = T1 x (D2/D1)^1.06 — it scales a known race time to a new distance. It works best between 5K and marathon.

How accurate is it?

Usually within a few percent for trained runners, less so for very different distances. General guidance, not medical advice.

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