Finish Time Calculator
Pace × distance.
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Running
Race Time Predictor
Predict your time at any distance from a recent race.
Predicted time
—
At target distance.
| Predicted pace | — |
|---|---|
| Known pace | — |
| Target distance | — |
| — |
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Enter your figures above to see the step-by-step working.
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How the Race Time Predictor Works
You can predict a race time at one distance from a result at another using Peter Riegel’s formula: the new time equals the old time multiplied by the ratio of distances raised to the power 1.06. That small exponent above 1 reflects the fact that you slow down slightly over longer distances. A 25-minute 5K predicts roughly a 1:55 half marathon.
It assumes similar training and conditions and works best for distances that aren’t too far apart. Real results vary with endurance, terrain and pacing.
predicted time = known time × (new distance ÷ known distance)^1.06
Frequently Asked Questions
How do you predict a race time?
Use Riegel’s formula: multiply your known time by the distance ratio raised to the 1.06 power.
What half marathon time does a 25-minute 5K predict?
Roughly 1 hour 55 minutes, assuming comparable fitness and conditions.
How accurate is the prediction?
Good for a ballpark, especially between nearby distances, but training, terrain and pacing shift the real result.
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