Training Calculator - Predict Your Marathon Time

In 1977, Pete Riegel devised a formula for predicting race times, based on your existing performances. The basic formula is t2 = t1 * (d2 / d1)1.06, but the "1.06" can be improved upon.

Specifically, when converting from half marathon to full marathon, it often provides what feels like an unobtainable time. From an analysis of over a thousand runners, we found that it was more than 5% out for two thirds of runners. We have produced a calculator that will give you a more realistic calculation - and it takes your gender into account. In our sample data, it got within 5% for three quarters of our sample.

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Enter your half marathon time here:


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