When to use this calculator
Estimate a different-distance race time with an explicit endurance-scaling exponent. Empirical scaling model, not a guaranteed performance. Training, conditions and distance range strongly affect validity.
Explore the pace, splits & race time calculators for other questions in this topic. For a related calculation, use the Route Climbing Density Calculator: Summarise how much total climbing is present per kilometre of a route.
PUTTING IT INTO PRACTICE
Riegel Race Time Predictor: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Known race time (minutes) | 50 |
| Known distance (km) | 10 |
| Target distance (km) | 20 |
| Chosen Riegel exponent | 1.06 |
| Result | 104.246576 minutes |
- Check the input labels and enter the example values above.
- Apply the relationship: Estimated time = known time × (target distance/known distance)^exponent.
- The result is 104.246576 minutes, rounded for display.
How to interpret your result
Empirical scaling model, not a guaranteed performance. Training, conditions and distance range strongly affect validity.
Use matching distance units and decimal minutes. A constant-pace plan does not forecast how terrain, conditions or fatigue will affect a race. A split is a time over a chosen reference distance.
Frequently asked questions
How do I read a result of 5.5 minutes per kilometre?
It means 5 minutes 30 seconds per kilometre, because 0.5 of a minute is 30 seconds.
When is the riegel race time predictor useful?
Estimate a different-distance race time with an explicit endurance-scaling exponent. Empirical scaling model, not a guaranteed performance. Training, conditions and distance range strongly affect validity.
How do I use the riegel race time predictor?
Enter known race time (minutes), known distance (km), target distance (km), chosen riegel exponent. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Estimated time = known time × (target distance/known distance)^exponent.
What should I check before using the result?
Empirical scaling model, not a guaranteed performance. Training, conditions and distance range strongly affect validity.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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