Race Time Predictor
Enter one recent race and see your predicted times across every standard distance, using Riegel’s proven endurance model.
| Distance | Predicted time | Pace |
|---|---|---|
| 5K | 23:58 | 7:44/mi |
| 10K | 50:00 | 8:04/mi |
| Half Marathon | 1:50:19 | 8:25/mi |
| Marathon | 3:50:00 | 8:47/mi |
How the prediction works
Predictions use Riegel’s formula: T₂ = T₁ × (D₂ / D₁)1.06. The 1.06 exponent reflects the reality that pace slows as distance grows. It’s most accurate when the predicted distance is reasonably close to the one you ran, and assumes you’ve trained specifically for the target race.
A predictor tells you what’s possible; a training plan gets you there. Marathon predictions in particular assume the endurance base to hold the pace — that’s exactly what a structured build provides.
Ready to train toward it?
Build a free, personalized plan that uses these paces and progresses you safely to race day.
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