Race predictor

One race time. Nine predictions.

Enter a recent race time and your effort level. See what it translates to at every distance from the 100m to the marathon, using Riegel's endurance exponent.

Your Reference Race

Enter a valid time (minutes and seconds are required).

Predictions assume similar training and conditions across distances — actual race results vary with terrain, weather, and event-specific training.

Predicted times at every distance
DistancePredicted time
RIEGEL T2 = T1 × (D2/D1)^1.06

How this prediction works

Riegel's endurance formula estimates how race times scale with distance for a trained endurance athlete. The 1.06 exponent reflects the fact that pace naturally slows over longer distances — it's a statistical pattern seen across thousands of race results, not a guarantee for any individual race.

Your effort percentage adjusts your reference time to a common baseline before the distances are compared, so a race you ran at 90% effort produces different (faster) predictions than the same time run all-out.

Before you trust the number

This tool estimates potential, not a promise. Sprint distances (100m–400m) rely more on raw power and technique than endurance pacing, so predictions get less reliable the further D2 is from your reference distance. Warm up properly before any time trial, and talk to a coach if you're building toward a specific race.

Racing a 400m specifically?

Turn your goal time into a four-segment pacing plan.

Open the 400m Split Calculator