Lean Body Mass Calculator: LBM from Height and Weight

Lean body mass and body fat percent by formula
Formula	Use	LBM	BF%
Boer	Standard clinical	54.7 kg	21.9%
James	Non-obese profiles	55.3 kg	21.0%
Hume	Broad population	51.1 kg	27.0%

Reading your lean body mass result

The dark panel is headline LBM; white cards add body fat %, functional mass ratio, composition, and (for adults) per-formula rows.

Example: male, 170 cm, 70 kg (metric defaults)

Adult cohort → headline LBM 53.7 kg (118.4 lb), body fat 23.3%, functional mass ratio 76.7%. Model comparison: Boer 54.7, James 55.3, Hume 51.1 kg with matching BF% columns. Composition bar: lean 53.7 kg, fat 16.3 kg.

Example: pediatric cohort ≤14 (Peters)

Same height and weight with cohort ≤14 (Peters) → Peters LBM about 52.5 kg; adult comparison table hidden. Body fat % still uses 100 − (LBM ÷ weight × 100) from that Peters value.

Manual body fat % vs headline LBM

Measured body fat % (dual-energy X-ray absorptiometry (DEXA), calipers, etc.) drives the body fat card and composition bar only. Headline LBM and functional mass ratio stay on Boer/James/Hume mean or Peters until you change height, weight, sex, or cohort.

Lean body mass calculator: Boer, James, Hume, and Peters

Estimate lean body mass (LBM) from height, weight, and sex. Adult mean of Boer, James, and Hume; cohort ≤14 uses Peters. Optional manual body fat % updates the fat readout and bar only. Educational only; not medical or dosing advice.

What this calculator does

The widget estimates lean body mass (LBM), weight minus storage fat, from height, weight, and sex. Cohort Adult averages Boer, James, and Hume; ≤14 (Peters) uses the pediatric estimate and hides the adult table. Body fat % defaults to 100 − (LBM ÷ weight × 100). Manual body fat % overrides the body fat card and composition bar only; headline LBM and functional mass ratio stay formula-based. No imaging, protein targets, or clinical testing.

Boer (male, W kg, H cm):

$\mathrm{LBM}=0.407W+0.267H-19.2$
James (male):

$\mathrm{LBM}=1.1W-128\,(W/H)^2$
Hume (male):

$\mathrm{LBM}=0.32810W+0.33929H-29.5336$
Peters (pediatric):

$e\mathrm{LBM}=3.8\times(0.0215\,W^{0.6469}\,H^{0.7236})$

LBM vs fat-free mass (FFM)

Lean body mass (LBM) counts essential fat in organs and nerves; fat-free mass (FFM) excludes all lipid (roughly 2–3% of weight in men, 5–12% in women). This page labels results as LBM on the dark panel and in the comparison table.

Accuracy and limits

Height-and-weight formulas are population averages and can miss unusual muscle, low muscle in older adults, or obesity (James especially). Spread across the three adult models at 70 kg, 170 cm male is about 4 kg; the mean is a range summary, not a measured lean mass. Manual body fat % improves the fat side of the composition bar when you have DEXA or field measurements; it does not change headline LBM. Not for medication dosing; basal metabolic rate (BMR) and total daily energy expenditure (TDEE) are not computed here.

FAQ

How is the headline LBM calculated for adults?

With cohort Adult, the dark results card averages Boer, James, and Hume on weight (kg) and height (cm) with sex-specific coefficients. Body fat % is 100 − (LBM ÷ weight × 100) from that headline value unless you enter manual body fat %. The Model comparison table lists each formula with its own implied body fat %.

What lean body mass do the metric defaults show?

Male, 170 cm, 70 kg, cohort Adult: headline LBM about 53.7 kg (118.4 lb), body fat about 23.3%, functional mass ratio about 76.7%. Table rows: Boer 54.7 kg, James 55.3 kg, Hume 51.1 kg; composition bar lean about 53.7 kg, fat about 16.3 kg.

When does the widget use the Peters formula?

Set cohort to ≤14 (Peters). Pediatric mode hides the adult comparison table and uses Peters only:

e\mathrm{LBM}=3.8\times(0.0215\,W^{0.6469}\,H^{0.7236})

(W kg, H cm). Sex still selects coefficients where the equation applies.

What does manual body fat % change?

A measured body fat % replaces the formula-derived body fat readout and recomputes the composition bar (lean and fat mass from weight). The dark-panel headline LBM and functional mass ratio still use the formula mean (or Peters). Leave the field blank to keep formula-derived body fat %.

What is functional mass ratio?

(Headline LBM ÷ weight) × 100. At the defaults it reads about 76.7%, which matches 100% − 23.3% body fat because both come from the same formula LBM. With manual body fat % active, body fat % follows your entry while functional mass ratio still tracks headline LBM.

Which formula is most accurate: Boer, James, or Hume?

None fits every build. Boer is the usual clinical default; James fits many non-obese adults but can skew with obesity; Hume is a broad linear baseline. At the defaults the three span about 4 kg (54.7 down to 51.1); the widget averages them for the headline instead of picking one.

Can I use this for medication dosing?

No. Some hospital protocols reference lean mass or adjusted body weight, but this page is educational only and does not replace prescriber or institutional dosing rules.

Sources & citations

References used for the calculation method and definitions. Links open in a new tab when available.

[1]

Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984;247(4 Pt 2):F632-F636

Boer formula for lean body mass estimation, used as the standard clinical LBM calculation method.

[2]

Janmahasatian S, Duffull SB, Ash S, et al. Quantification of lean bodyweight. Clin Pharmacokinet. 2005;44(10):1051-1065

Pharmacokinetic modeling paper on predicting fat-free mass / lean bodyweight from sex, height, and weight; cites James W. (Research on Obesity, HMSO 1976) and situates classic anthropometric LBM estimates used in clinical dosing alongside newer approaches.

[3]

Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966;19(4):389-391

Hume linear LBM formula using height and weight, providing a broad population baseline for lean mass estimation.

Fitness Reference Note

Informational Use: These calculations (BMI, Calories, etc.) are based on standard statistical formulas and are intended for general reference and goal-setting purposes only.

Consult Experts: This tool does not provide medical advice, diagnosis, or treatment. Results may not be accurate for athletes, pregnant individuals, or those with underlying health conditions.

Health Safety: Always consult with a healthcare professional or qualified trainer before beginning any new diet or intensive exercise program.

Privacy First: All calculations are performed locally in your browser. No health data is stored or transmitted to any server.

Lean Body Mass Calculator: LBM from Boer, James, and Hume

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