How does the Riegel formula work?

T2 = T1 × (D2/D1)^1.06. The exponent 1.06 (fatigue factor) accounts for the physiological fact that longer races are run at lower intensity. A 5K personal best can be used to predict marathon time.

Is the Riegel formula accurate for all distances?

The formula is most accurate for predicting within two to three times the known race distance. Extrapolating from a 1-mile time to a full marathon introduces large errors because the energy systems and training requirements differ significantly.

How does predicted vs actual marathon time typically compare?

The Riegel formula tends to predict optimistic marathon times for runners who are not specifically marathon-trained. Adding 5-8% to the predicted time gives a more realistic estimate for most recreational runners.

Race Time Predictor Riegel Formula

Predict race finish time for any distance using the Riegel formula: T2 = T1 × (D2/D1)^1.06, allowing projection from known race performances to target distances.

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Frequently Asked Questions

How does the Riegel formula work?

Is the Riegel formula accurate for all distances?

How does predicted vs actual marathon time typically compare?