What this calculator tells you
The Riegel model adjusts a known performance for the fact that pace usually slows as distance increases. It is useful for realistic planning when recent effort and target event are reasonably similar.
How to use the Race Time Predictor
- 1
Enter a recent hard effort or race distance and time.
- 2
Enter the target distance in the same unit.
- 3
Use the result as a pacing reference, not a promise.
Formula and interpretation
Method
Predicted time = known time × (target distance ÷ known distance)^1.06.
How to read the result
Treat the result as a neutral benchmark. Training specificity, terrain, weather, fueling, and pacing can move actual performance substantially.
Important limitations
The fixed exponent is a population rule of thumb, not your personal endurance profile. Predictions become less reliable across very different distances.
Race Time Predictor questions
Can a 1 km effort predict a marathon?
The calculation works, but such a large distance jump is unlikely to represent endurance, fueling, and durability accurately.
Should the known effort be recent?
Yes. A recent, well-paced performance under comparable conditions is more informative.
