Tool
Race Pace Predictor
Enter one recent race time and see two predictions for every other distance — Daniels VDOT (favoured for short-jumps) and Pete Riegel's log-scale model (slightly more honest for extrapolating to the marathon).
| Distance | Daniels VDOT | Riegel (k=1.06) | Pace |
|---|---|---|---|
| 5 km | 21:42 | 21:35 | 4:20/km |
| Half marathon | 1:39:44 | 1:39:17 | 4:44/km |
| Marathon | 3:27:15 | 3:27:01 | 4:55/km |
Why two models?
Daniels VDOT and Riegel disagree most when you extrapolate across many doublings of distance. VDOT assumes your fractional VO₂max stays constant; Riegel assumes a power-law relationship. For a 5K-to-marathon prediction, VDOT is typically optimistic by 2–4 % and Riegel is the more honest bound.
What about the course and weather?
Both predictions assume a flat, certified course in mild conditions. To convert a flat-course prediction into a race-specific target with elevation, heat, and humidity adjustments, use TrainingFlow's full race-day pacing engine.