Lean Body Mass Calculator
Calculate your Lean Body Mass (LBM) to find out how much of your body weight consists of muscles, bones, and organs.
Composition Results
Fat vs Lean WeightsComposition Math Ready
Provide your age, height, and weight to calculate clean lean tissue mass ratios and see comparative scientific outputs.
What is Lean Body Mass (LBM)?
Lean Body Mass (LBM) constitutes the total weight of your body excluding all lipid fat tissues. Specifically, LBM is composed of skeletal muscle fibers, vital organs (heart, brain, kidneys, liver), bone minerals, water content, connective tissues, and blood fluids.
While LBM is often used to estimate metabolic requirements, it is vital to remember that LBM is not identical to Muscle Mass. Muscle mass represents only a fraction of your overall LBM, meaning that increases in bone density, cellular hydration, or organ size can also increase your LBM without necessarily building skeletal muscle tissue.
Boer vs. James vs. Hume Formulas
These three historical algorithms predict lean tissue mass using statistical height and weight cohorts. While the Hume Formula is highly robust, the James Formula is known to slightly over-penalize extreme obesity, and the Boer Formula remains the most frequently referenced tool in clinical pharmacology to adjust safe medicine dosing for active body tissues.
Methodology & Formula: Boer Formula
Standard Reference Calculations
Muscular Adult Male
Active Adult Female
Frequently Asked Questions
Get answers to common queries based on clinical literature and fitness research.
Lean mass contains your muscle, which is metabolically active tissue. Knowing your LBM helps you accurately customize your daily protein targets and design precise hypertrophy training and fat loss regimens.
Lean Body Mass includes everything in your body that is not fat (bones, vital organs, blood, connective tissue, water, and skeletal muscle). Skeletal muscle is just one component of LBM, though it is the easiest one to change through strength training.