Race predictor
Tell us one race time. See what you could run at any other distance. No sign-up.
We add about 2% to marathon predictions, because the last 10 km catch out most runners. Treat this as your best day.
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How the prediction works
We use Riegel’s formula, a long-standing way of estimating race times, published by the engineer Peter Riegel. It assumes you slow down by a steady amount as the distance goes up. The formula tends to run fast for the marathon, so we add about 2% to marathon times. A 25:00 5K predicts about 52:07 for 10K, 1:55:00 for the half and 4:05:03 for the marathon.
The prediction assumes you’ve trained for the longer distance and that the course and the weather are kind. Use your most recent race on a flat course, because an old time or a hilly one will throw it off.