How the Marathon Time Predictor Works
Our marathon time predictor uses the globally recognized formula created by research engineer Peter Riegel. His model helps runners accurately approximate what they could physically achieve at new distances, assuming proper specialized training.
The Riegel Formula explained:
T2 = T1 x (D2 / D1)^1.06
Where T1 is your given time for your recent race distance (D1), and T2 is the predicted time for the target marathon distance (D2). Simply enter a recent race time that accurately represents your peak fitness. Using a Half Marathon or 10K time typically gives the most accurate Marathon prediction, as a 5K race primarily tests your VO2 max rather than extreme endurance.
Why Your Predicted Time Might Not Match Reality
While the mathematical prediction is a great starting point for your pacing bands and race day strategy, completing a 26.2 mile race requires physiological adaptations that math can't guarantee:
- Training Volume: A good 10K prediction assumes you've actually completed the required high-mileage marathon training plan.
- Fueling Strategy: Proper carbohydrate loading and mid-race nutrition are vital to hit predictions without bonking at mile 20.
- Weather and Elevation: The calculator assumes your goal race has similar weather and terrain to your baseline race.
Want to manually calculate a different pacing strategy? Check out our Running Pace Calculator & Split Generator.