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Grade-Adjusted Pace (GAP) Calculator
Convert hill pace to flat-equivalent effort, and back.
What grade-adjusted pace tells you
Grade-adjusted pace (GAP) is the flat-ground pace that would cost the same energy as the pace you actually ran on a hill. It lets you compare a hilly run to a flat one, and pace climbs by effort rather than by the misleading number on your watch — your true pace always slows uphill even when you are working just as hard.
The Minetti model
It uses Minetti’s measured energy cost of running across gradients: Cr(i) = 155.4·i⁵ − 30.4·i⁴ − 43.3·i³ + 46.3·i² + 19.5·i + 3.6 J/kg/m, where i is the grade as a decimal. Flat running costs about 3.6 J/kg/m. Your flat-equivalent pace is your actual pace scaled by 3.6 ÷ Cr(i): uphill costs more, so the equivalent flat pace is faster.
Why downhill isn’t free
The energy cost of running bottoms out around a −10% to −15% grade. Beyond that, braking forces make steep descents cost more again — which is why the curve turns back upward and a very steep downhill can be nearly as costly as climbing.
Questions
What is grade-adjusted pace?
GAP is the flat-ground pace that would cost the same energy as the pace you actually ran on a hill. It lets you compare a hilly run to a flat one, and pace climbs by effort instead of by the misleading number on your watch.
How is it calculated?
It uses Minetti’s measured energy cost of running at different gradients. Uphills cost more energy per metre, so your flat-equivalent pace is faster than your hill pace; gentle downhills cost less, but steep downhills cost more again from braking.
Is faster always better downhill?
No. The energy cost of running bottoms out around a −10% to −15% grade; beyond that, braking forces make steep descents cost more and beat up your legs, which is why the model turns back upward.