Predict your time at a target distance from a known performance (Riegel formula).
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Peter Riegel's formula: T₂ = T₁ × (D₂/D₁)1.06. Accounts for natural pace degradation over longer distances.
| Target distance | Predicted time | Pace |
|---|---|---|
| 10K | 52min 07s | 5:13/km |
| 15K | 1h 20min 07s | 5:20/km |
| 21.1K (half marathon) | 1h 55min 00s | 5:27/km |
| 30K | 2h 47min 01s | 5:34/km |
| 42.2K (marathon) | 3h 59min 47s | 5:41/km |
| 50K | 4h 47min 02s | 5:44/km |
The Riegel formula assumes appropriate training for the target distance. Without marathon-specific preparation, your real time will be slower than the prediction.
Peter Riegel's formula (1977) predicts your time at a target distance from a known performance. The exponent 1.06 accounts for the natural pace degradation that occurs over longer distances — the principle that nobody runs a marathon at their 5K pace.
T₂ = T₁ × (D₂/D₁)^1.06
Riegel is most accurate for distances 2× to 4× your reference. For example: a known 10K predicts your half marathon very well. Predicting a marathon from a 5K is less reliable — marathon-specific training has a big impact on the real time.
Once you have your target time, use our pace calculator to break it down into race pace, and our route planner to map a training route.
