Lean Body Mass Calculator
Lean and fat mass (kg) from weight and body fat %.
How it works
Lean = weight × (1 − body-fat%); Fat = weight × body-fat%
Lean mass includes muscle, bone and water; it is key for metabolism and training progress.
Worked example
Weight 70 kg at 17% body fat: LBM = 70 × (1 − 0.17) = 58.1 kg, fat mass ≈ 11.9 kg.
Dropping to 15% at the same weight implies slightly more lean mass; in real cuts, a small LBM loss is more typical.
Notes and limitations
LBM depends on the body-fat estimate, and home scales are noisy, so do not over-trust the absolute number. It is most useful for tracking trends or sizing protein intake (per kg of LBM is more precise than per kg of body weight).