Race time predictor
Enter a recent race to predict your time at every other distance, and see where each prediction would place you among US finishers.
Enter a recent race time to see your predictions.
Common questions
How does the race time predictor work?
It uses Riegel's formula, the most widely used race-time predictor: time₂ = time₁ × (distance₂ ÷ distance₁)^1.06. The exponent above 1 accounts for slowing down as races get longer.
How accurate are race time predictions?
They're best between nearby distances, like a 10K from a 5K. Marathon predictions from short races assume you've done the long runs and mileage for a marathon; most recreational runners finish a few minutes to a quarter of an hour slower than predicted.
Which race should I use to predict my marathon time?
A recent half marathon run all-out is the best guide. A 10K is next best. Use a race from the last couple of months, on a flat course in cool weather.