Lean Body Mass & Percentage Calculator
Estimate your lean body mass in kilograms and as a percentage of body weight using the Boer formula, from your sex, weight and height.
How it works
Men: LBM = 0.407·weight(kg) + 0.267·height(cm) − 19.2 · Women: LBM = 0.252·weight + 0.473·height − 48.3
Lean body mass (LBM) is your total weight minus its fat content, so it captures muscle, bone, organs and body water. The Boer equation estimates it from sex, weight and height and is one of the more accurate population formulas. Expressing lean mass as a percentage of total weight gives an at-a-glance sense of body composition, and its mirror image is an implied body-fat percentage. Because it excludes fat, LBM is often the better base for setting protein targets or scaling certain medication doses.
Worked example
A 75 kg, 178 cm man: LBM = 0.407·75 + 0.267·178 − 19.2 = 30.5 + 47.5 − 19.2 = 58.8 kg, which is 58.8 ÷ 75 = 78.4% lean, implying about 21.6% body fat.
Frequently asked questions
How is lean body mass different from muscle mass?
Lean body mass includes muscle but also bone, organs, connective tissue and the water in them. Skeletal muscle is only part of it — roughly half of lean mass in a typical adult — so LBM is always larger than muscle mass alone.
Why estimate lean mass instead of measuring it?
Direct measurement needs a DEXA scan or hydrostatic weighing. The Boer formula gives a good estimate from three numbers you already know, which is enough for tracking trends and setting nutrition targets.
Should I base my protein intake on lean mass?
Many coaches do, because fat tissue needs little protein to maintain. Targeting grams of protein per kilogram of lean mass (rather than total weight) avoids overestimating needs for people carrying more fat.
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Educational estimate, not medical advice — for personal health decisions consult a qualified healthcare professional.