Race Time Predictor (Riegel Formula) 10K to Half Marathon Prediction
Estimate a half marathon time from a 50-minute 10K result, typical for runners stepping up in distance.
Estimate race performance at a new distance based on a known race result using the Riegel formula. Enter your Known Race Time, Known Race Distance, Target Race Distance to get an instant predicted race time. Formula: known_time * pow((target_distance / known_distance), 1.06).
Predicted Race Time
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How It Works
How It Works
This calculator estimates how long it will take you to complete a new race distance based on a previous race result. It uses the Riegel formula, which adjusts your known race time to predict performance at a different distance.
The formula increases the time proportionally based on how much longer (or shorter) the new distance is, using a standard endurance adjustment factor of 1.06.
- Enter your known race time in minutes.
- Enter the distance of that race in kilometers.
- Enter the new target race distance in kilometers.
- The formula scales your time using (Target Distance ÷ Known Distance) raised to the power of 1.06.
Understanding the Results
The result shows your predicted finishing time in minutes for the target distance. It assumes similar fitness, pacing, and race conditions.
This is an estimate, not a guarantee, but it provides a realistic benchmark for planning and goal setting.
- The output is displayed in total minutes.
- Longer distances will usually produce proportionally longer times.
- Shorter distances will result in faster predicted times.
- Use the result to plan pacing and set race goals.
Disclaimer
This calculator provides estimates for informational purposes only. It is not professional advice. Verify results with a qualified professional. Disclaimer.