Marathon Predictor: What Your Half Marathon Time Really Means
A recent race is the best honest starting point for a marathon goal. This predictor turns it into a finish estimate with a classic formula.
What is the Marathon Finish Predictor?
Enter a recent race distance and finish time, then pick a target distance. The tool applies the Riegel formula, which scales time by the distance ratio raised to 1.06, and shows an estimated finish in hours and minutes. This is an estimate, not a guarantee: course profile, weather, and training all move real results away from any prediction.
How to use it
- Enter your recent race distance in kilometres.
- Enter that race finish time in minutes.
- Pick your target race and click Predict My Finish.
Worked example
A 110-minute half marathon predicts about 229.31 minutes (3h 49m) for a marathon: 110 x (42.195/21.1)^1.06 = about 229.31 minutes.
How long would a 110-minute half marathon predict for a marathon?
About 3 hours 49 minutes. The Riegel formula scales the 110 minutes by the distance ratio raised to 1.06, giving roughly 229 minutes, which is an estimate rather than a promise.
Frequently asked questions
Is the prediction guaranteed?
No. It is an estimate from one formula; hills, heat, and training can shift a real finish by many minutes.
Why 1.06?
That exponent is the standard Riegel value used for endurance running predictions, balancing fatigue over longer distances.