Free tool
Race Time Predictor
Enter a recent race and your finish time, and the calculator predicts what you can run for every distance from 1 mile to the marathon, with your training paces. A 25 minute 5K predicts about 52:07 for 10K, 1:55:00 for the half and 3:59:45 for the marathon.
- 1 mile to marathon
- Training paces included
- Based on a recent race
Predicted race times
Your training paces
How does the race predictor work?
It uses the Riegel formula, the same race equivalency method used in the Hansons Marathon Method calculators. Your predicted time is your race time multiplied by the distance ratio raised to the power of 1.06. For the mile and 3K the power is 1.08, and for 2 miles it is 1.07. Every distance is predicted from the one race you enter.
The training paces come straight from those predictions. Easy, moderate and long runs are set from your marathon pace. Speed work sits between 5K and 10K pace, VO2 max work between 3K and 5K pace, and threshold runs between 10K and 20K pace. If your 10K is 40 minutes or faster, threshold runs move to between 10 mile and half marathon pace.
How accurate is a race time predictor?
For distances close to the race you entered, it is usually very close. The further you predict, the more it depends on training. A 5K time predicts your marathon only if you have done the long runs and the weekly kilometres. Most first marathoners run a few minutes slower than the prediction.
Which race should I enter?
Use your most recent race, run on a flat course in good weather, at full effort. A half marathon is the best predictor of a marathon. If your race was hot or humid, put it through the race weather calculator first and use the ideal conditions time.
Questions runners ask
How do I predict my marathon time from a 5K?
Enter your 5K time in the calculator. It multiplies your time by the distance ratio to the power of 1.06. A 25 minute 5K predicts about a 4 hour marathon, if your training supports it.
What half marathon time do I need for a 4 hour marathon?
About 1:55. The predictor shows a 1:55 half is equivalent to a marathon of just under 4 hours.
What is the Riegel formula?
A race time equation published by Peter Riegel. Time 2 equals time 1 multiplied by distance 2 divided by distance 1, to the power of 1.06.
Why is my marathon slower than predicted?
Predictions assume full endurance training. Without enough long runs and weekly kilometres, or on a hot day, most runners finish slower than the prediction.
What training paces should I use?
Use the paces in the second table. Keep easy runs truly easy, and only run speed, VO2 max and threshold paces in planned sessions.
How often should I update my race prediction?
After every race, or every 6 to 8 weeks with a time trial. Update your training paces when your fitness improves.
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