Lean Body Mass Calculator
Estimate your lean body mass (everything except fat) and fat mass from your height and weight, using the widely cited Boer formula.
\ud83d\udcaa Build and keep lean mass
Learn moreWhat lean body mass tells you
Lean body mass is your total weight minus fat — muscle, bone, organs and water. It is useful for setting protein targets, dosing some medications, and tracking whether weight changes are fat or muscle. Men typically carry a higher lean-mass share than women. This uses the Boer formula, a solid estimate from height and weight without a body-composition scan.
How it’s calculated & sources
Boer formula (metric): men LBM = 0.407 times kg plus 0.267 times cm minus 19.2; women = 0.252 times kg plus 0.473 times cm minus 48.3. Fat mass = weight minus LBM; results converted to pounds.
Benchmark: Boer formula (1984), a standard lean-body-mass estimator; typical lean-mass share about 75 to 90 percent (higher in men, lower at higher body fat).
Results update as you type and are general estimates, not personalized advice. Verify with a professional.
Worked example
A 170-lb, 5 foot 8 man has an estimated lean body mass around 128 lb (about 76% of weight), leaving roughly 42 lb of fat mass.
Frequently asked questions
Is this as accurate as a DEXA scan?
No — formulas estimate from height and weight and cannot see your actual composition. A DEXA or hydrostatic test is more precise.
Why estimate lean mass?
It helps set protein intake, judge whether weight loss is fat vs muscle, and personalize fitness goals.
Which formula is best?
Boer is a common, well-validated choice; James and Hume are alternatives. They agree closely for most adults.