Lean Body Mass Calculator
Calculate your lean body mass using the Boer, James, and Hume formulas.
Lean body mass estimates are approximate and do not replace professional assessment.
Lean body mass calculator
Estimate lean body mass using body-fat or formula-based methods.
Body fat percentage gives a more direct estimate when available.
Estimated lean body mass
64.0 kg
Approximate lean body mass based on entered values.
Estimated fat mass
16.0 kg
Lean mass percentage
80.0%
Method used
Body fat percentage method
Uses standard lean body mass estimation formulas. Reviewed for accuracy. Estimate only. Does not replace medical, dietetic, or professional fitness advice.
Personalized interpretation
Your estimated lean body mass is 64.0 kg.
Lean body mass includes muscle, bone, organs, water, and other non-fat tissue.
Fat mass is estimated separately from lean mass based on entered values and selected formula.
Formula-based estimates may differ from clinical measurement methods.
This result should be used as broad body composition context, not a diagnosis or fixed target.
Lean body mass vs fat mass
Lean body mass
64.0 kg
Includes all estimated non-fat tissue.
Fat mass
16.0 kg
Estimated fat tissue based on entered values.
What lean body mass includes
Lean body mass is not the same as muscle mass alone.
Lean mass formulas and methods
Body-fat method
Uses body fat percentage directly to estimate fat mass and lean mass.
Boer formula
Uses height, weight, and sex to estimate lean body mass.
James formula
Another commonly used height-and-weight estimate.
Hume formula
A lean body mass estimate that may differ from other formulas.
Lean body mass vs muscle mass
Lean body mass
Includes muscle, organs, bones, water, connective tissue, and all non-fat tissue.
Muscle mass
Refers specifically to muscle tissue, which is only one part of lean body mass.
How lean body mass is used
Limitations and healthy context
Lean body mass estimates can vary because of hydration, formula choice, body composition, and measurement differences.
Clinical tools such as DEXA scans may provide more detailed assessment. Consider speaking with a qualified healthcare professional if you have health concerns.
Formula explanation
Fat Mass = Body Weight × Body Fat PercentageLean Body Mass = Body Weight − Fat MassMen Boer: LBM = 0.407W + 0.267H − 19.2Women Boer: LBM = 0.252W + 0.473H − 48.3Men James: LBM = 1.1W − 128 × (W ÷ H)²Women James: LBM = 1.07W − 148 × (W ÷ H)²Example: 80 kg at 20% body fat
Fat mass = 80 × 0.20 = 16 kg. Lean body mass = 80 − 16 = 64 kg.
Example: 180 lb at 25% body fat
Fat mass ≈ 45 lb. Lean body mass ≈ 135 lb.
Frequently Asked Questions
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