Running

Race Time Predictor

Predict a finish time at a new distance from a recent race result.

How it works. Riegel formula: T₂ = T₁ × (D₂⁄D₁)^1.06. Assumes similar effort and good endurance base; longer extrapolations are rougher. Common: 5K=5, 10K=10, half=21.0975, marathon=42.195 km.