Lean Body Mass Calculator

Calculate your lean body mass (LBM) — the weight of everything in your body except fat. Used for accurate protein targets, medication dosing, and body composition tracking.

Your details 4 formulas
lbs
ft
in
%
Enables the most accurate method
FAQs
What is lean body mass vs. fat-free mass? ›
Lean body mass (LBM) is sometimes used interchangeably with fat-free mass (FFM), but they differ slightly. FFM is your total body weight minus all fat. LBM is total body weight minus storage fat — it includes essential fat (found in cell membranes, bone marrow, and organs). Practically, the difference is small — LBM is typically 2–3% higher than FFM because it retains essential fat. For most purposes (protein intake, medication dosing, fitness planning), the formulas on this page provide a useful estimate.
Why does lean body mass matter? ›
LBM is used for: (1) Protein intake — base protein targets on LBM rather than total weight for more accurate muscle-building targets; (2) Drug dosing — many medications (anesthetics, antibiotics, chemotherapy) are dosed by LBM to avoid over-dosing in obese patients; (3) Metabolism — metabolic rate correlates more closely with LBM than total weight; (4) Katch-McArdle BMR formula uses LBM for the most accurate calorie calculation; (5) Fitness tracking — monitoring LBM over time is the true measure of muscle gain and fat loss progress.