What is Riegel's formula for predicting race times?

Riegel's formula: T2 = T1 × (D2/D1)^1.06. The 1.06 fatigue factor accounts for the exponential difficulty of longer distances. Predicting marathon from 10K: if 10K = 40:00 (4:00/km), marathon prediction ≈ 3:29 (4:58/km).

How accurate are marathon time predictions from shorter race results?

Predictions are most accurate when training is marathon-specific and the predictor race is recent. Half marathon is the best predictor (within ~2–5 minutes). Using 5K or 10K paces often underestimates the difficulty of marathon-specific fatigue, especially after 30km.

Marathon Finish Time Predictor

Predict marathon finish time from recent race results using Riegel's formula, VO2max estimates, and training load metrics. Generate pacing strategies for target finish times.

Use the full interactive calculator below, or

Related Calculators

Lactate Threshold Pace

Sports

Chronic Training Load (CTL)

Sports

Marathon Finish Time Predictor

Related Calculators

Frequently Asked Questions

What is Riegel's formula for predicting race times?

How accurate are marathon time predictions from shorter race results?