Race Time Predictor
The Riegel formula predicts finish times at other distances from one recent race, assuming similar training and conditions.
How to use
- Choose the distance of your recent race.
- Enter your finish time.
- Predicted times for the other standard distances appear instantly.
Note
Uses the Riegel formula: T2 = T1 x (D2 / D1)^1.06. Predictions assume endurance training matched to the target distance — a 5K time alone will over-predict marathon performance without long-run training. Estimate only — not medical advice.
Frequently Asked Questions (FAQ)
How does the Race Time Predictor work?
It uses the Riegel formula (T2 = T1 times (D2 divided by D1) to the power 1.06) to predict 5K, 10K, half marathon and marathon times from one recent race result.
Is the prediction guaranteed?
No. It assumes similar fitness and conditions at the longer distance, so treat it as an estimate, not a guarantee.
What recent result do I need to enter?
The distance and your finish time of a recent race, for example your latest 10 km time. From that single result it predicts your 5K, 10K, half marathon and marathon times.
Which distances can it predict?
5 km, 10 km, half marathon and marathon, whichever you pick as the target.