Lean Body Mass Calculator
0 lb lean body mass
How This Calculator Works
This calculator estimates lean body mass (LBM) — everything in your body that isn't fat, including muscle, bone, organs, and water — using the Boer formula, one of the most widely cited equations in exercise physiology for this purpose. The Boer formula is sex-specific because men and women carry different average proportions of essential fat and muscle at the same height and weight:
Men: LBM = (0.407 × weight in kg) + (0.267 × height in cm) − 19.2
Women: LBM = (0.252 × weight in kg) + (0.473 × height in cm) − 48.3
Estimated body fat percentage is then simply the remainder: (weight − LBM) ÷ weight. Because this method relies only on height and weight, it's a quick population-level estimate rather than a direct measurement — it doesn't account for individual differences in frame size, muscularity, or fat distribution.
A Common Misconception
Lean body mass is not the same as muscle mass. LBM includes bone, organs, water, and connective tissue alongside skeletal muscle, so two people with identical lean body mass can have noticeably different amounts of actual muscle. If you want a closer look at your fat percentage specifically, the body fat calculator uses body circumference measurements, which generally track body composition more directly than weight-and-height formulas alone.
Using Your Result
Lean body mass is often used to set more personalized nutrition targets, since protein needs scale better with lean mass than with total body weight. Once you have your LBM, the protein calculator can help translate it into a daily protein target. As with any formula-based estimate, this is meant for general educational and fitness-planning purposes, not a clinical measurement — for precise body composition assessment or health decisions, talk to a doctor or a qualified professional.
Frequently Asked Questions
What formula does this lean body mass calculator use?
It uses the Boer formula, a sex-specific equation widely used in exercise physiology: for men, LBM = (0.407 x weight in kg) + (0.267 x height in cm) - 19.2; for women, LBM = (0.252 x weight in kg) + (0.473 x height in cm) - 48.3. It estimates LBM from just height and weight, so it's a quick approximation rather than a direct measurement.
Is lean body mass the same as muscle mass?
No. Lean body mass includes muscle plus bone, organs, water, and connective tissue, so it's always higher than muscle mass alone. Two people with the same lean body mass can have different amounts of actual muscle, which is why LBM is better used as a general body-composition metric than a direct muscle-mass indicator.