🏅 Race Time Predictor
Use a recent race or time trial to predict what you could run at other distances, from 1 mile to the marathon.
Predicted times
How the Race Time Predictor works
The Riegel formula scales your time by the distance ratio raised to the power 1.06, which accounts for slowing down over longer distances.
T₂ = T₁ × (D₂ ÷ D₁)^1.06
Step-by-step calculation
- 1Choose a recent race and enter your time.
- 2Apply the Riegel formula to other distances.
Worked example
A 25:00 5K predicts about 52:07 for 10K, 1:55:00 for a half marathon and 3:59:47 for a marathon.
Race Time Predictor examples
| Minutes | Predicted times |
|---|---|
| 13 | Marathon ≈ 2:04:41 |
| 19 | Marathon ≈ 3:02:14 |
| 25 | Marathon ≈ 3:59:47 |
| 31 | Marathon ≈ 4:57:19 |
| 38 | Marathon ≈ 6:04:28 |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Race Time Predictor?
Set realistic goals for your next race.
Important factors that can affect your results
- Training for the longer distance.
- Course and weather.
- Pacing strategy.
Frequently asked questions
How accurate is it?
It works best when you have trained for the longer distance. Marathon predictions are often optimistic without enough long runs.
Which race should I enter?
A recent all-out effort gives the best prediction.
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Last reviewed November 2026 · How we build and check our tools · Report a problem