Lean Body Mass

Estimating Lean Mass from Height, Weight, and Gender

Lean body mass is your total body weight minus fat mass — everything else, including muscle, bone, organs, and water. Enter your gender at birth, height, and weight, and this calculator shows the estimate from three different published formulas side by side — plus their average — since no single formula is more “correct” than the others.

The Formulas

Every formula below uses the same two inputs — weight (kg) and height (cm) — with different coefficients for men and women, so the same two colors track the same two quantities across all three:

Boer (1984) — derived from a large study population and the most widely cited of the three today:

$$\vC{\text{Men: LBM}} = 0.407 \times \vA{\text{Weight}} + 0.267 \times \vB{\text{Height}} - 19.2$$ $$\vC{\text{Women: LBM}} = 0.252 \times \vA{\text{Weight}} + 0.473 \times \vB{\text{Height}} - 48.3$$

James (1976) — uses a BMI-like weight-to-height-squared ratio instead of treating height and weight as separate terms:

$$\vD{\text{Men: LBM}} = 1.10 \times \vA{\text{Weight}} - 128 \times \left(\frac{\vA{\text{Weight}}}{\vB{\text{Height}}}\right)^2$$ $$\vD{\text{Women: LBM}} = 1.07 \times \vA{\text{Weight}} - 148 \times \left(\frac{\vA{\text{Weight}}}{\vB{\text{Height}}}\right)^2$$

Hume (1966) — the oldest of the three, still frequently used in clinical medication-dosing contexts:

$$\vE{\text{Men: LBM}} = 0.3281 \times \vA{\text{Weight}} + 0.33929 \times \vB{\text{Height}} - 29.5336$$ $$\vE{\text{Women: LBM}} = 0.29569 \times \vA{\text{Weight}} + 0.41813 \times \vB{\text{Height}} - 43.2933$$

Worked Example

A 180 cm (5’11”), 80 kg man:

1. Boer: $0.407 \times \vA{80} + 0.267 \times \vB{180} - 19.2 = \vC{61.4} \text{ kg}$
2. James: $1.10 \times \vA{80} - 128 \times (\vA{80}/\vB{180})^2 = \vD{62.7} \text{ kg}$
3. Hume: $0.3281 \times \vA{80} + 0.33929 \times \vB{180} - 29.5336 = \vE{57.8} \text{ kg}$
4. Average: $(\vC{61.4} + \vD{62.7} + \vE{57.8}) \div 3 = 60.6 \text{ kg}$ — about 75.8% of total body weight.

Key Factors to Consider

• Lean body mass and fat-free mass are nearly, but not always, treated as identical terms. Some sources define lean body mass as including a small amount of essential fat (found in bone marrow, organs, and the nervous system) while “fat-free mass” excludes essential fat entirely — in practice the two terms are frequently used interchangeably, and these population-based formulas estimate the same general quantity either way.
• These formulas were derived from average-body-composition study populations, which is exactly why muscular or very lean individuals see more disagreement between them. A bodybuilder with unusually high muscle mass, or someone with unusually low body fat, falls outside the range these regression formulas were built from — the spread between the three results tends to widen for anyone whose body composition differs substantially from an average adult.
• Lean body mass is a useful reference point for setting protein intake targets. Many evidence-based protein recommendations for muscle building or maintenance are expressed per pound or kilogram of lean body mass rather than total body weight, since lean tissue — not fat — is what actually uses dietary protein for repair and growth.
• None of these formulas can distinguish muscle from other lean tissue. “Lean body mass” lumps together muscle, bone, organs, and water — two people with the identical lean mass figure could have very different amounts of actual muscle, which this calculator alone can’t reveal.

Common Mistakes

• Treating one formula’s result as the single “correct” answer. All three formulas are legitimate published estimates with no formula proven more accurate than the others — the spread between them, not any one number, is the honest picture.
• Applying these formulas to a body type far outside the original study populations. Bodybuilders, very lean athletes, and others with atypical body composition will see wider disagreement between the three formulas, since none were derived from populations like theirs.
• Confusing lean body mass with muscle mass. Lean body mass includes bone, organs, and water alongside muscle — a higher lean mass figure doesn’t necessarily mean more muscle specifically.
• Setting protein or calorie targets from a rough formula estimate instead of a direct measurement when precision actually matters. For general reference this estimate is fine, but someone tracking body composition closely should weigh it against an actual measurement like the Body Fat Percentage Calculator’s circumference method.

Useful to Know

• Want a body-fat-percentage-based estimate instead of a formula based purely on height and weight? The Body Fat Percentage Calculator calculator uses circumference measurements for a more individualized number.
• Setting a protein intake target based on your lean mass? The Protein Intake Calculator calculator translates a lean-mass figure into a daily protein target.
• Curious how your lean mass estimate stacks up against a healthy weight range for your height? The Ideal Weight Calculator calculator covers that separate question.