Race Time Predictor
Predict your 10K, Half Marathon and Marathon finish times based on your current performance.
0 h · 25 min · 30 sec
How does the prediction work?
We use the Riegel formula (T₂ = T₁ × (D₂/D₁)^1.06), a classic endurance model that assumes relatively consistent pacing ability across distances. For the marathon we use a slightly higher exponent (~1.10), because the standard formula is often too optimistic for recreational runners at that distance. Enter a recent 5K, 10K or half result to see estimates for 10K, half and marathon.
When does it work best?
It works best with consistent training and a recent near-maximal race effort (not an easy workout). Predicting longer distances from shorter races is usually more useful than the reverse. If you are still building marathon volume, treat the prediction as a training target — not a finish-line guarantee.
What affects prediction accuracy?
Aerobic base, weekly mileage, elevation, weather, nutrition, sleep and racing experience all affect how close predictions match reality. Accumulated fatigue, extreme heat or hilly courses can add minutes. Use the reference table on this page for typical ranges and cross-check with the pace calculator for race pace.
When should you use this predictor?
Use the predictor to set realistic goals, plan training blocks and estimate marathon pace from a recent 5K or 10K. Pair it with Zone 2 for volume and intervals for VO₂ stimulus. Recalculate every 4–8 weeks as your times improve.
Reference race time equivalencies
| 5K time | 10K | Half | Marathon |
|---|---|---|---|
| 20:00 | 41:30 | 1:31 | 3:29 |
| 22:00 | 45:40 | 1:40 | 3:50 |
| 25:00 | 52:00 | 1:55 | 4:21 |
| 27:30 | 57:20 | 2:07 | 4:47 |
| 30:00 | 1:02 | 2:20 | 5:13 |
Frequently asked questions about race predictions
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