RACE STRATEGY & PERFORMANCE LAB
Race Time Predictor (Riegel Formula)
Extrapolate your recent race times to longer distances using the gold-standard Peter Riegel model. Set realistic Sub-2 HM and Sub-4 Marathon goals backed by real data.
Enter Current Race Performance
Select your benchmark distance and enter your actual finish time to predict other distances using the Riegel formula.
Equivalent Race Times Based on 5K Performance
Projected 10K, Half Marathon, and Marathon times using standard Riegel fatigue scaling:
| Current 5K Time | Predicted 10K | Predicted Half Marathon | Predicted Marathon | Target Benchmark |
|---|---|---|---|---|
| 20:00 (Pace 4:00) | 41:35 | 1:32:05 | 3:11:45 | Sub 3:15 Marathon |
| 22:30 (Pace 4:30) | 46:47 | 1:43:35 | 3:35:43 | Sub 3:45 Marathon |
| 25:00 (Pace 5:00) | 51:59 | 1:55:06 | 3:59:41 | Sub 4:00 Marathon / Sub 2 HM |
| 27:30 (Pace 5:30) | 57:11 | 2:06:37 | 4:23:40 | Sub 4:30 Marathon |
| 30:00 (Pace 6:00) | 1:02:23 | 2:18:07 | 4:47:38 | Sub 5:00 Marathon |
| 35:00 (Pace 7:00) | 1:12:47 | 2:41:08 | 5:35:34 | Marathon Finisher |
Frequently Asked Questions About Race Time Prediction
Understand the mathematical limits and aerobic training required to hit predicted times.
How does the Peter Riegel race predictor formula work?
Developed by research engineer Peter Riegel in 1977, the formula states: T2 = T1 × (D2 / D1)^1.06, where T1 is your known time over distance D1, and T2 is the predicted time for distance D2. The 1.06 fatigue exponent accounts for natural slowdown as distance increases.
What conditions are required for accurate 5K-to-Marathon predictions?
Riegel assumes you have built adequate weekly mileage and completed progressive long runs (25km+) specific to the marathon distance. Without sufficient aerobic base and fat-burning adaptations, muscle fatigue and glycogen depletion will cause slowdown beyond the formula prediction.