🦴 Lean Body Mass Calculator
Calculate your fat-free body mass
Written by Albert Mateos · Founder & Editor
Last reviewed: May 2, 2026
How it works
Calculate your lean body mass (everything except fat) using the Boer, James, and Hume formulas. Know exactly how much of your weight is muscle, bone, water, and organs vs fat. Essential for tracking body composition changes during cuts or bulks.
How to Use This Calculator
- Enter your weight in kg or lbs.
- Enter your height in cm or ft/in.
- Select your biological sex.
- Review your estimated lean body mass (LBM) and fat mass.
Example
Inputs: Male, 180 cm, 80 kg
Result: LBM: 66.9 kg, Fat mass: 13.1 kg (~16% body fat)
What it means: An LBM of 67 kg on an 80 kg male suggests a lean, athletic build with healthy body fat around 16%.
Tips
- LBM includes muscle, bone, organs, and water — not just muscle.
- Track LBM over time to ensure you're preserving muscle during a cut.
- Protein intake should be calculated per kg of LBM, not total body weight, for lean individuals.
- The Boer formula is most accurate for adults with normal body composition.
Disclaimer: This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
Learn More
Frequently Asked Questions
- What is lean body mass and why does it matter?
- Lean body mass is your total body weight minus all fat mass, including muscles, bones, organs, water, and connective tissue. It is a more useful metric than total weight for assessing fitness because two people at the same weight can have very different body compositions. Higher lean mass is associated with a faster metabolism, better insulin sensitivity, and greater functional strength.
- How does the Boer formula calculate lean body mass?
- The Boer formula estimates lean body mass using your height and weight with sex-specific coefficients. For men the formula is 0.407 times weight in kg plus 0.267 times height in cm minus 19.2, and for women it is 0.252 times weight plus 0.473 times height minus 48.3. It is one of the most validated estimation formulas and performs well across a wide range of body types.
- How can I increase my lean body mass?
- Progressive resistance training combined with adequate protein intake (1.6 to 2.2 grams per kilogram of body weight) is the most effective way to increase lean mass. Prioritize compound movements like squats, deadlifts, and presses, and ensure you are eating at or slightly above maintenance calories. Consistent training over months and years produces the most significant and sustainable gains.