Calculate your lean body mass — the weight of everything in your body except fat — using multiple validated formulas.
Lean body mass (LBM) is the total weight of your body minus all fat. It includes muscle, bone, organs, water, and connective tissue. It's a more useful fitness metric than total body weight because it tells you how much of your weight is metabolically active tissue.
Your basal metabolic rate (BMR) is driven almost entirely by your lean mass — muscle tissue burns far more calories at rest than fat tissue. Knowing your LBM helps set accurate protein targets, calibrate calorie needs, and track whether you're gaining muscle or losing it during a diet.