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Riegel's Formula
Origin & History
Pete Riegel, a research engineer and marathon runner, developed this formula in 1977. It was first published in Runner's World magazine. The formula has become the standard for race time prediction because of its simplicity and general accuracy across different distances.
The Formula
Predicted Time =
T2 = T1 × (D2 / D1)^1.06
• T1 = Recent race time
• D1 = Recent race distance
• D2 = Target race distance
• T2 = Predicted time
The exponent 1.06 is an average fatigue factor. Higher values (e.g., 1.08) may be used for runners with less endurance base.