Predict
Marathon time predictor
Your recent race
MetricSplit ladder
Equivalent efforts- Half Marathon1:38:104:39 /km
Your entered race is marked; every other row is projected from it.
Worked example
A 44:30 10K projects to a 3:24:43 marathon at 4:51/km. With a longest run of 28 km that expected figure holds; under 21 km the conservative end moves out past 3:45, and that is the number to plan against.
Common questions
- How accurate is a marathon prediction from a 10K?
- Accurate within a few minutes for athletes with a genuine marathon build behind them. For runners whose speed outpaces their endurance base it commonly over-predicts by ten minutes or more — the error is almost always in the optimistic direction.
- Which race should I enter for the best prediction?
- The closest distance to your target that you have raced recently and honestly. A half marathon predicts a marathon far better than a 5K does, because it tests more of the same endurance.
- Why is my predicted pace slower than my 10K pace?
- Sustainable pace falls as distance rises. Riegel models that decay with an exponent of 1.06, which is why a marathon pace lands well below 10K pace even for a well-trained runner.
- Does this account for hills, heat, or course profile?
- No. It projects from one flat-course performance to another. Heat, elevation and wind all cost time on top of this estimate.