Race predictor
One race result, every other distance projected. Riegel formula plus the VDOT score that powers your training paces.
Predicted race times
| Distance | Time | pace (min/mi) |
|---|---|---|
| 1 Mile | 6:37 | 6:37 |
| 5K · your race | 22:00 | 7:05 |
| 10K | 45:52 | 7:23 |
| 15K | 1:10:30 | 7:34 |
| Half Marathon | 1:41:12 | 7:43 |
| Marathon | 3:31:00 | 8:03 |
Accuracy drops for distances much shorter or longer than your input race, and for runners not specifically trained for the target distance.
How this calculator works
- Riegel formula
The Riegel formula projects a finish time at one distance (T₂) from a known time at another (T₁) using T₂ = T₁ × (D₂/D₁)^1.06. The 1.06 exponent captures the typical fatigue curve for trained runners. PaceCalc uses 1.06 as the default; you can adjust the exponent on the race-predictor page if you fade harder than average.
R. H. Riegel, "Athletic Records and Human Endurance," American Scientist, vol. 69, no. 3, 1981, pp. 285–290.
- VDOT and equivalent training paces
VDOT is a single number that summarizes your aerobic fitness from a recent race performance. Daniels' tables map VDOT to equivalent times at every standard distance and to recommended paces for easy, marathon, threshold, interval, and repetition work. PaceCalc estimates VDOT from your inputs, then surfaces those equivalent paces.
Jack Daniels, Daniels' Running Formula, 3rd edition, Human Kinetics, 2013. Tables for VDOT and zone-based pacing.
- The Riegel projection assumes you race two distances within roughly the same training cycle and at similar fitness. Predictions across very different distances (5K to marathon) carry more uncertainty than 10K-to-half projections.