Marathon Time Predictor
Free online Marathon Time Predictor that runs directly in your browser.
-
1Enter data
Enter content, paste text or load a file from disk. -
2Click the button
The tool will immediately process your data in the browser. -
3Get the result
Copy the finished text or save the file to your device.
return "Result ready in 0.1s";
}
Rate this tool:
Related tools
Other tools you may find usefulMarathon Time Predictor - Calculate Your Potential
Marathon Time Predictorestimates your potential marathon result based on your recent results over shorter distances (5K, 10K or half marathon). A tool for runners planning their first or next marathon.
What is the marathon time prediction based on?
Marathon predictors are based on mathematical models of running performance. The most popular formulas are:Riegel's formula(1977): T2 = T1 × (D2/D1)^1.06, where T1 is the time for the distance D1 and T2 is the predicted time for D2. The exponent of 1.06 takes into account the fact that longer distances require proportionally more time.Pete Riegel's formulais the standard in running predictions - used by coaches, Garmin, Strava and many other running platforms.
How to use the predictor?
Select your reference distance (5km, 10km or 21km half marathon) and enter your latest result. The closer your reference run was to the marathon and the better your form, the more accurate the prediction will be. The predictor provides: estimated marathon time, mile pace (min/km), mile pace (min/mile), and recommended race pace for a negative split.
Why is a marathon harder than math predicts?
Mathematical predictions assume that you are in as good shape and condition as you were during the reference run. However, a marathon has specific challenges: a "wall" around 30-35 km when muscle glycogen is depleted, cumulative leg fatigue after 35+ km of running, weather conditions (temperature above 15°C slows down significantly), hydration and nutrition strategy (energy gels every 45 min), training preparation (appropriate training cycle of at least 16-20 weeks).
How to improve your real marathon result?
To get closer to your expected time: ensure adequate training volume (minimum 50-70 km/week at peak), train at marathon pace (tempo runs), test gels and energy drinks during long training runs, plan a negative split (the second half faster than the first), start slower than you think you should.
Frequently Asked Questions
How accurate is marathon time prediction?
Prediction is approximate - the difference between predicted and actual results is typically ±5-10% for well-prepared runners. The error increases with lack of specific marathon training, extreme weather, stomach problems and tactical errors. Riegel's formula works best for runners with a 5K time of less than 25 minutes.
What reference distance gives the most accurate prediction?
The half marathon (21 km) gives the most accurate prediction of the marathon because it is closest to the target distance and requires a similar energy strategy. The 10km result is the second most accurate. The 5K result may overpredict if the runner is "sprint-like" - fast over short distances, but without marathon endurance.
What is a "wall" in a marathon and how to avoid it?
Hitting the wall is a sudden depletion of energy around 30-35 km, caused by the depletion of muscle glycogen. How to avoid: start slower than the target pace (the first 10 km 10-15 sec/km slower), regularly consume gels/drinks every 30-45 minutes from the 45th minute of the run, ensure proper glycogen loading 2-3 days before the start (carb loading).
How many weeks of preparation do you need for a marathon?
A standard marathon training plan lasts 16-20 weeks. For beginners and slower runners (over 5 hours), 16 weeks is enough. For runners aiming for sub-4 hours. — 18–20 weeks. Key elements: weekly long runs (up to 30-35 km), tempo training, threshold runs and adequate recovery.
How to calculate running pace in min/km?
Running pace = total time / distance. For the marathon 4:00:00 (240 minutes) / 42.195 km = 5:41 min/km. Our predictor automatically converts your result into a minute pace and suggests a recommended pace for each kilometer. You can also set the pace directly - the calculator will calculate the marathon time.