Race time predictor
Predict your 5K, 10K, half marathon and marathon times from one recent race, using the VDOT and Riegel formulas — with a note on racing in Bangkok's heat.
| Distance | Predicted (VDOT) | Pace | Predicted (Riegel) |
|---|---|---|---|
| 5K | 24:06 | 4:49 /km | 23:59 |
| 10K | 50:00 | 5:00 /km | 50:00 |
| Half marathon | 1:50:52 | 5:15 /km | 1:50:19 |
| Marathon | 3:49:34 | 5:26 /km | 3:50:01 |
Your VDOT is about 40.0. Predictions assume you've trained for the distance and race in cool conditions — in Bangkok, allow extra time for heat.
How it works
VDOT (Daniels & Gilbert) estimates your aerobic fitness from a race and converts it to other distances. It's the main prediction.
Riegel uses T2 = T1 × (D2 ÷ D1)^1.06 — a simple rule that works well between nearby distances.
Predictions assume you've trained for the target distance. Marathon predictions from a 5K are often optimistic unless you've done the long runs.
FAQ
How accurate are race time predictions?
Usually within a few percent between similar distances (5K to 10K). From short races to the marathon they're less reliable, because the marathon depends on endurance training.
Which race should I enter?
Use a recent, all-out race on a flat course in cool weather. The closer it is to your target distance, the better.
How much slower will I be in Bangkok?
Often 3–8% on a typical humid morning. Our heat pace calculator estimates it for the conditions.
Results are estimates for planning training, not medical advice.