Predict Your Half marathon Time From a Marathon

How a Marathon predicts your Half marathon

Going from a marathon to a half marathon is a confident prediction, because you are working back to a shorter distance from a race that already proves deep endurance. Your half pace should be clearly faster than your marathon pace, since you only have to hold it for half the time and there is no wall to manage.

In fact many runners can race a half faster than this prediction suggests, because a marathon is run conservatively to survive the distance, while a half can be attacked. If your marathon was well paced, the predicted half is a floor you should comfortably beat with a sharper, more aggressive effort.

Your half should outrun half your marathon

Riegel multiplies your marathon by about 0.48 to reach the half, predicting a time a little faster than a flat halving. A 3:30 marathon points to roughly a 1:40 half. That jump reflects the freedom of a shorter race, you can run nearer your threshold the whole way instead of holding back for fuel and muscular reasons.

The reason real halves often beat the prediction is that marathon pacing is deliberately cautious. You leave a margin so you do not blow up at 20 miles. A half has no such cliff, so you can spend that margin. Use your marathon as a conservative half estimate, then race the half a touch braver.

If you are racing the half soon after a marathon, give your legs real recovery first. Marathon fatigue lingers for weeks and will mask the speed this prediction promises. Rested and sharpened with a little faster work, most runners comfortably beat the number, which is exactly what you want from a shorter, more aggressive race.

Want every distance at once? The race pace predictor shows your time for the whole range and prints a pace band, and the VDOT calculator turns this race into your training paces.