Race Weight Calculator

About this calculator

Race weight is the body weight — usually a modest deficit from training weight — at which an endurance athlete carries the least mass without sacrificing the lean tissue that produces power, calculated by holding lean body mass constant and lowering only the fat-mass component to a target body-fat percentage. It is not the same as simply “losing weight,” because dropping muscle along with fat can lower running economy and power output even as the number on the scale improves.

Distance runners, cyclists and triathletes use race-weight calculations in the final build phase before a goal event, since carrying excess fat mass over race distance costs measurable time — a commonly cited rule of thumb is roughly 1-2 seconds per mile per pound of bodyweight for runners on hilly courses, though the effect is smaller on flat terrain. Because it targets a specific, achievable body-fat percentage rather than an arbitrary number, it also helps flag when a “goal weight” is unrealistic for a given frame and lean mass.

This calculator takes your current weight, current body-fat percentage and target race-day body-fat percentage, and returns your race weight along with an estimate of the time it could save.