Lean Body Mass Calculator
Calculate lean body mass from height and weight using the Boer formula.
- Lean Mass57.1 kg · 79%
- Fat Mass15.4 kg · 21%
Lean mass makes up about 79% of your total body weight.
- Estimated Fat Mass15.4 kg
The Boer formula estimates lean mass from height and weight alone — it doesn't account for individual muscle or frame differences, so treat it as a starting estimate.
ƒShow your work
LBM = 0.407×kg + 0.267×cm − 19.2
- 1Total weight = 72.6 kg, Height = 175 cm
- 2Lean Body Mass = 57.1 kg
- 3Estimated Fat Mass = Total weight − LBM = 15.4 kg
About the Lean Body Mass Calculator
Lean body mass is everything on the scale that isn't fat — muscle, bone, organs, water, connective tissue, all of it — and this calculator estimates it from height and weight using the Boer formula, one of a handful of equations built to approximate it without a scan. It's a formula-based estimate, not a direct measurement, so it can't separate how much of your lean mass is muscle versus water or organ weight the way a DEXA scan can.
Strength athletes and bodybuilders use lean mass numbers to set protein targets (often per pound or kilogram of lean mass rather than total weight) and to track whether a bulk or cut is adding or losing the right kind of tissue, not just moving the scale in either direction.
This runs entirely in your browser using just the height and weight you enter — nothing about your body stats is stored or sent anywhere, and there's a quick note before the numbers: this is a formula estimate, not a body-composition scan or medical measurement.
How it’s calculated
The Boer formula (1984) was developed as an update to older lean-mass equations and uses different constants for men and women: LBM = 0.407×kg + 0.267×cm − 19.2 for men, and 0.252×kg + 0.473×cm − 48.3 for women. The differing coefficients reflect that, at the same height and weight, men and women tend to carry different average proportions of muscle versus fat.
Other formulas — James (1976) and Hume (1966) among them — use slightly different constants and can produce results a kilogram or two apart for the same person, which is normal; all of them are population-average approximations rather than a measurement of your specific composition.
Frequently asked questions
What is lean body mass?
It's your total body weight minus fat mass — so muscle, bone, organs, water and connective tissue combined, not muscle mass alone. A body with more lean mass at the same total weight generally reflects a leaner, more muscular build.
Is lean body mass the same as muscle mass?
No — lean mass includes muscle but also bone, organs and body water, so it's always higher than muscle mass alone. There's no way to isolate muscle specifically from height and weight; that requires imaging like a DEXA or MRI scan.
Why does the formula use different constants for men and women?
Because at the same height and weight, men and women tend to have different average ratios of muscle to fat, so the Boer formula's coefficients are fit separately by sex to better match typical body composition for each.
How do I use lean body mass to set a protein target?
A common approach is to aim for roughly 0.7–1 gram of protein per pound of lean body mass per day for those focused on muscle retention or growth — though needs vary by training volume, goals and individual factors.
Is this formula accurate for very lean or very heavy individuals?
It's less reliable at the extremes — formulas like Boer were fit to average body types, so someone who is exceptionally lean, very muscular, or has a high body fat percentage may see a larger gap between the estimate and their real lean mass.
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