Conventional running wisdom puts the cost of unused body weight at about 2 seconds per pound per mile. Climbing costs more per pound than flat ground — Fatlytics adjusts for your race's elevation gain using a peer-reviewed running-economy model, not just the flat rule alone.
—
Educational estimate only, not a training or medical guarantee. The flat-ground rate (2 sec/lb/mile) is the widely cited running-community heuristic; the elevation adjustment scales that rate using Minetti et al. (2002), "Energy cost of walking and running at extreme uphill and downhill slopes," calibrated so a 0 ft-gain course reduces to the flat rule exactly. Assumes a uniform average grade across the course, which will over- or under-estimate courses with very uneven terrain. Individual results vary with fitness, pacing, and course profile.