Health
Lean Body Mass Calculator
Pick a method, enter the inputs, and the calculator returns lean body mass, fat mass, and estimated body fat percentage. Body fat % is the most accurate; Boer, James, and Hume give regression-based estimates from height and weight.
Method
Unit
From a body-fat measurement (Navy method, calipers, DEXA, etc.).
Methods
- Body fat %: the most direct. Multiply weight by (1 - body fat %).
- Boer (1984): regression from height and weight.
- James (1976): uses height-to-weight squared ratio.
- Hume (1966): classic regression equation, still commonly cited.
Formula-based estimates can disagree by several pounds. They are educational estimates, not DEXA scans or medical measurements.
Lean body mass
147.6 lb (66.95 kg)
Fat mass 32.4 lb (14.7 kg); est. body fat 18%
If you have a direct body-fat measurement, the Body fat % method is the most accurate. The formula-based methods agree within a few pounds for most healthy adults but diverge at the high and low ends of body composition.
Examples
180 lb at 18% body fat
LBM ≈ 147.6 lb, fat 32.4 lb
Boer, male, 180 lb, 70 in
LBM ≈ 156 lb
James, female, 140 lb, 65 in
LBM ≈ 102 lb
Hume, male, 200 lb, 72 in
LBM ≈ 173 lb
How it works
The body-fat method is direct: LBM equals weight times (1 minus body fat percentage). The formula methods derive LBM from height and weight using regression equations published decades ago.
Body fat % · LBM = weight x (1 - bf%)
Boer (male) · 0.407 x weight_kg + 0.267 x height_cm - 19.2
James (male) · 1.1 x weight_kg - 128 x (w/h)^2
Hume (male) · 0.3281 x weight_kg + 0.33929 x height_cm - 29.5336
Female versions use different coefficients in each formula.
Related health calculators
- Body fat calculator for the body fat % input via the U.S. Navy circumference method.
- Ideal weight calculator for healthy weight ranges via Hamwi, Devine, Robinson, and Miller.
- BMI calculator for the standard BMI category, which is a height-and-weight metric (not lean mass).
- Protein intake calculator when you want to scale daily protein to lean body mass instead of total weight.
- All health calculators.
Frequently asked questions
Lean body mass (LBM) is your total body weight minus your fat mass. It includes muscle, bone, organs, connective tissue, and the water in those tissues. It is often used as a base for protein targets and drug dosing.
If you have a body-fat percentage from a reasonable measurement (Navy circumference, skinfold calipers, DEXA, bioimpedance), the Body fat % method is the most direct. The formula methods (Boer, James, Hume) only use height and weight, so they cannot account for individual body composition.
Each formula was derived from a different population sample. Boer (1984), James (1976), and Hume (1966) all return slightly different values, especially at the extremes of body weight. Use them as a range, not a single number.
No. DEXA (dual-energy X-ray absorptiometry) is a clinical body composition measurement. The formulas on this page are population-level estimates from height, weight, and (optionally) a body-fat percentage. They are educational estimates only.
Common uses include scaling protein intake to lean mass instead of total weight, tracking changes during fat loss or muscle gain, and as a sanity check against scale weight when body composition is shifting.
No. The calculator is an educational tool. Body composition matters for many health questions, but interpreting the number for clinical purposes is the job of a clinician or registered dietitian.
Related calculators
Health
TDEE Calculator
Estimate your Total Daily Energy Expenditure from sex, age, height, weight, and activity — with maintenance, cut, and bulk targets.
Health
BMI Calculator
Compute Body Mass Index from height and weight, with the standard category scale and the healthy weight range for your height.
Health
BMR Calculator
Estimate your Basal Metabolic Rate — the calories your body burns at rest — using the Mifflin–St Jeor equation.