Previsão Tempo Maratona (Riegel)

Riegel formula: predicting race times across distances

The Riegel formula was published by Pete Riegel in 1977 and is the most widely used equation to predict a race time at one distance from a known time at another. It is written as T₂ = T₁ · (D₂ / D₁)1.06, where T₁ is the known time over distance D₁ and T₂ is the predicted time over D₂. The exponent 1.06 reflects the fact that pace gets slightly slower as distance grows — endurance fatigues runners non-linearly. Example: a runner who runs 5 km in 22:00 is predicted to run a marathon in roughly 3:31:45. The formula works best for athletes with a solid endurance base; it tends to underestimate pure speed athletes (sprinters extending up) and overestimate well-trained marathoners (who hold pace better than 1.06 predicts).

Applications: race planning and training decisions

Used for race-day pace planning (project realistic marathon goal from a recent 10 km or half-marathon), marathon training (set long-run paces from current fitness), and inside Strava, Garmin Connect and Runalyze as the default predictor. Also useful for choosing between race distances when registration windows force a decision months ahead.

FAQ

Why exponent 1.06? Riegel derived it empirically from thousands of race results across running, swimming and cycling. Values between 1.05 and 1.08 work for trained runners.

Is it accurate for the marathon? Only if your endurance base matches. A 5K specialist with little long-distance training will fall short of the prediction; marathon-specific training is required.

Which input distance is best? The closer the input to the target, the better. Predicting a marathon from a half-marathon is far more reliable than from a 5K.

Are there alternatives? Yes — Cameron's formula, VDOT (Daniels) tables and Purdy points all produce similar results, often within 1-2% of Riegel.