Race Time Predictor
Predict finish times for any distance based on a recent race result.
Enter Your Recent Race
How This Works
This uses the Riegel formula: T2 = T1 × (D2/D1)^1.06. It accounts for the fact that you slow down over longer distances. The formula is most accurate when predicting from a race distance close to your target (e.g., 10K → half marathon).
Accuracy Tips
- Use a recent race result (within last 4-6 weeks) for best predictions
- Predictions from 5K to marathon are less reliable than 10K to half
- Add 2-3% for your first race at a new distance (pacing inexperience)
- Hot weather, hilly courses, and wind will slow you vs these predictions