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How the Riegel formula works
Peter Riegel, an American research engineer and marathoner, observed in 1981 that elite and recreational runners alike slow down with distance along a near-power law: T₂ = T₁ × (D₂ ÷ D₁)^1.06. The exponent 1.06 means doubling the distance costs about 9% more time per kilometer. It is a statistical fit over many runners, not physiology, but it tracks real race results remarkably well from the mile up to the marathon when training matches the goal event.
Reading the prediction honestly
The formula assumes you have trained for the target distance. It is optimistic for a 5K specialist attempting their first marathon without long runs, and slightly conservative for a high-mileage marathoner racing a 10K. Heat, hills, altitude, and crowding at the start line all push actual results slower than the model. Use the number as a pacing anchor — run the first third of a goal race at or a touch slower than the predicted pace, then judge how much is left.
Contexto local: España
Datos locales de España, útiles para cálculos cotidianos:
- IVA: 21 % general (10 % hostelería, 4 % alimentos básicos), siempre incluido en el precio.
- Moneda y pagos: Euro (€); tarjeta sin contacto y Bizum muy extendidos.
- Unidades y números: Sistema métrico; coma decimal y punto de millar: 1.234,56 €.
- Nóminas: Costumbre de 14 pagas (extra en julio y diciembre) en salarios y algunas rentas.
- Propina: Voluntaria, 5–10 % o redondeo; el servicio va incluido en el precio.
Actualizado: octubre 2026 · valores de 2025, fuentes oficiales arriba.
Preguntas frecuentes
Which recent race gives the best prediction?
A hard, recent, all-out effort at a distance close to your target. A parkrun 5K from last weekend predicts far better than a hilly half marathon from two years ago, because fitness drifts and tough courses inflate times.
Why 1.06 and not another exponent?
Riegel fitted 1.06 to world-record and club-runner data; it remains the standard because it matches observed fatigue between roughly 3 km and the marathon. Jack Daniels’ VDOT tables use essentially the same curve, while some predictors raise it toward 1.08 for first-time marathoners.