Marathon Time Predictor
Free marathon time predictor
Enter a recent race result and we'll estimate your marathon and half marathon times. No login needed.
Estimated with the Riegel model from your recent race, assuming marathon-specific endurance and a flat, cool course. A hilly or hot course will be slower - check any race's real impact with the difficulty calculator.
Personalised prediction from your Strava training
For a prediction tuned to your actual fitness rather than a single race, connect Strava and we'll model your training.
Log In to Get Your Prediction
Log in and connect your Strava account to receive your personalised marathon time prediction.
Log InHow to predict your marathon time
The simplest way to predict a marathon time is from a recent race over a shorter distance. The widely used Riegel formula estimates your time at a new distance as T₂ = T₁ × (D₂ / D₁)1.06, where the 1.06 exponent reflects the natural slowdown as distance increases. In practice your marathon time is a little more than double your half marathon time - not exactly double - because fatigue and fuelling have a bigger impact over 42.2km.
Rough equivalent finish times
| Half marathon | Predicted marathon |
|---|---|
| 1:30 | 3:08 |
| 1:45 | 3:39 |
| 2:00 | 4:11 |
| 2:15 | 4:42 |
| 2:30 | 5:13 |
These are estimates for a runner with marathon-specific endurance on a flat course in good conditions. Your real time depends heavily on the course and the day - which is why a one-size-fits-all calculator is often optimistic.
What actually affects your marathon time
- Endurance & long-run volume - the biggest factor beyond raw speed.
- Course elevation - climbing slows you far more than descents help.
- Race-day temperature - every degree above ~15°C can cost 1-2%.
- Surface - trail and mixed courses run 10-20% slower than road.
- Pacing & fuelling - going out too fast is the classic marathon mistake.
Use the marathon difficulty calculator to see how a specific course and its weather would change your target time versus a flat, cool, road marathon.
How the Strava-powered prediction works
For a prediction tuned to you rather than a generic formula, Statathon analyses your Strava training history - combining a physiological running model with machine learning to account for your fitness, training volume, and race-distance performance.
What we look at
- Personal bests across multiple distances
- Weekly training volume over the past 6 months
- Training load and intensity patterns
- Recent fitness trends and progression
The personalised prediction works best with at least 6 months of consistent Strava data and a mix of shorter and longer runs.