🏃 Race Predictor – Running Time Calculator
Use a recent race result to predict your finish time for another distance, using the widely used Riegel formula for running performance.
How the Prediction Works
This calculator uses the Riegel formula, a widely used method in running science for estimating race performance across distances from a known result. It assumes that endurance performance degrades in a predictable, non-linear way as distance increases.
The formula is: T2 = T1 × (D2 / D1)^1.06, where T1 and D1 are the time and distance of your recent race, and T2 and D2 are the predicted time and target distance. The exponent of 1.06 reflects that running pace naturally slows somewhat as distance grows, based on decades of race-time data across many runners.
- Predictions are most accurate when your known race distance is reasonably close to your target distance.
- The formula assumes similar training, pacing, and race-day conditions (weather, terrain, elevation) for both distances.
This tool is intended for general training and race-planning purposes. Actual results can vary based on fitness, course difficulty, weather, and pacing strategy on race day.