Enter the pace you actually ran and the grade, and get the flat-ground pace that represents the same effort.
Uses the Minetti et al. (2002) running energy-cost model. Most accurate for grades roughly between −30% and 30%; very steep or very short grades vary more with terrain and footing.
GAP converts the pace you actually ran on a hill into the flat-ground pace that represents the same physical effort, so you can compare hilly and flat running fairly.
Only up to a point. Running downhill gets metabolically cheaper as the grade steepens, roughly down to somewhere around -15% to -20%, after which braking forces make it costlier again. This calculator's underlying model captures that curve rather than assuming downhill is always "free" speed.
Different platforms use different underlying models, so exact numbers can vary. This calculator uses a published exercise-science model (Minetti et al., 2002) rather than any specific watch or app's proprietary formula.
No, only grade/slope is modeled. Altitude, temperature, humidity, and surface conditions also affect effort but aren't included here.