Marathon Race Predictor

The Riegel formula is accurate to within ±5–10% for well-trained runners predicting across similar distances. Accuracy decreases with large distance gaps (e.g. 5K to marathon) or when the input race was not run at maximum effort.

T2 = T1 × (D2/D1)^1.06, where T1 is your known finish time, D1 is the known distance, D2 is the target distance, and T2 is the predicted time. The exponent 1.06 accounts for the increasing effect of fatigue over longer distances.

Yes, but the prediction will be less accurate. The formula works best with input races closer to the target distance. For marathon prediction, a recent 10K or half marathon result will give the most reliable estimate.

Beginner: 4:30–5:30 | Intermediate: 3:30–4:30 | Advanced: under 3:30 | Elite: under 2:30. The average marathon finish time is around 4:30 for men and 4:55 for women.

Use the pace column for your target distance to set your per-kilometer strategy. For example, if your predicted marathon pace is 5:30/km, aim to run the first half slightly slower (5:35/km) and negative split the second half.