💪 Lean Body Mass (LBM) Calculator
Calculate your lean body mass (fat-free mass) and Fat-Free Mass Index (FFMI) using the Boer, James, and Hume medical equations. 100% free.
Free No Signup Required Browser-Based
Estimated Lean Body Mass (LBM)
60.6 kg
Body Fat: 24.2% (19.4 kg) • Fat-Free Mass Index (FFMI): 18.7
Formula Comparisons
Boer Formula (1984)
61.4 kgJames Formula (1976)
62.7 kgHume Formula (1966)
57.8 kgHow to Use Lean Body Mass (LBM) Calculator
- Select your gender and unit system (Metric or Imperial)
- Enter your current total weight and height
- Review your estimated lean body mass, body fat percentage, and FFMI score
📖 Technical Encyclopedia & Standards Reference
Calculate your lean body mass (fat-free mass) and Fat-Free Mass Index (FFMI) using the Boer, James, and Hume medical equations. 100% free. This tool computes outputs according to official open technical and scientific specifications.
✓ Open Standards AlignmentCompliant with ISO/IEC, W3C, NIST, and standard mathematical formulations.
✓ 100% Client-Side / SecureZero server logging. Computations execute entirely in your local browser sandbox.
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Frequently Asked Questions
What is Lean Body Mass (LBM)?
Lean Body Mass is the total weight of your body minus the weight of your body fat, consisting of muscle, bone, organs, connective tissue, and water.
What is a good Fat-Free Mass Index (FFMI)?
An FFMI of 18–20 is average, 20–22 is athletic, and 22–25 represents top natural bodybuilding muscularity.