Running · race equivalency
Race equivalency calculator
Put in a recent race result and compare the same performance across standard running distances. No dead external link, no account, no motivational sermon from a watch.
Known performance
Advanced: fatigue exponent
1.06 is the classic Riegel value. Lower values preserve speed better as distance rises; higher values impose more fatigue. This is an equivalency model, not a substitute for distance-specific training.
Equivalent performance
T₂ = T₁ × (D₂ ÷ D₁)k
The calculator uses Peter Riegel’s endurance relationship, published in American Scientist in 1981. It is most useful when the known and target performances are both genuine endurance efforts and the runner is comparably trained for both distances.
Equivalent times
| Distance | Equivalent time | Pace / mile |
|---|
Race equivalency is not prophecy. Hills, heat, wind, course surface, fatigue, fueling, injury, and whether you actually trained for the target distance all remain stubbornly real.