The detailed guide below is currently available in English.
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.
Repères pour la France
Repères locaux pour la France, utiles dans les calculs du quotidien :
- TVA: 20 % en taux normal (5,5 % alimentaire, 10 % restauration) ; les prix sont TTC par loi.
- Monnaie & paiements: Euro (€) ; paiement sans contact et carte bancaire très répandus, virement SEPA instantané en développement.
- Unités & nombres: Système métrique ; virgule décimale et espace pour les milliers : 1 234,56 €.
- Santé: Carte Vitale ; l'Assurance Maladie rembourse en base ≈ 70 % des soins, le reste par mutuelle.
- Pourboire: Service compris : aucun pourboire obligatoire ; arrondir suffit.
Mis à jour : octobre 2026 · valeurs 2025, sources officielles ci-dessus.
Questions fréquentes
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.