Lean Body Mass Calculator

Calculate your lean body mass (LBM) and body fat mass. See ideal LBM ranges based on gender and weight.

This is a subtraction, not an estimate. You supply a body fat percentage you already measured somewhere else — calipers, a smart scale, a DEXA scan — and the tool splits your weight into the fat share and everything else. At the defaults, 20 percent of 70 kg is 14 kg of fat mass, leaving 56 kg of lean mass, which covers muscle, bone, organs, connective tissue and body water together rather than muscle alone. The LBM Percentage row is worth understanding before you trust it: because it divides lean mass by total weight, the weight cancels out algebraically and the figure is always exactly one hundred minus the body fat percentage you typed. Changing your weight from 70 kg to 100 kg leaves it at 80 percent. Only the fat percentage moves it. The Ideal LBM Range is a rule-of-thumb band scaled off your weight, not off your measurements: entering 1 in the Gender field takes 70 to 90 percent of body weight, and any other entry takes the 60 to 80 percent band, so a stray 2 or a blank silently selects the second band. The Height field is collected but never enters any displayed result — no formula here reads it, so changing it does nothing. Accuracy is inherited: a caliper reading off by three points shifts your reported lean mass by about two kilograms at this weight.