Compare multiple estimates
See Boer, James and Hume side by side instead of relying on one equation.
Health & wellness
Lean body mass calculator
Adult lean body mass estimate from sex, height and weight using Boer, James and Hume, plus an optional body-fat-derived comparison.
Profile and measurements
Boer (1984) is the primary result. James and Hume are shown alongside it so you can see the spread between methods.
Sex used by the formulas
Height
If you already have a reliable estimate, enter it to calculate weight × (1 − body fat %).
Your estimated lean body mass
Estimated lean body mass
kg
Primary result · Boer formula (1984)
Compare anthropometric formulas
Boer (1984)
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James (1976)
-
Hume (1966)
-
Spread across the three estimates: -
Method & sources
Boer is the primary result because it is a later published anthropometric equation than Hume and James and is widely reused for height-and-weight lean-mass estimation. James and Hume remain visible to show model variability. If body-fat percentage is entered, a fourth value is calculated directly from body weight without replacing Boer.
Formula
Boer — Male: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2 · Female: 0.252 × weight + 0.473 × height − 48.3. James — Male: 1.10 × weight − 128 × (weight/height)² · Female: 1.07 × weight − 148 × (weight/height)². Hume — Male: 0.32810 × weight + 0.33929 × height − 29.5336 · Female: 0.29569 × weight + 0.41813 × height − 43.2933. With BF%: LBM = weight × (1 − BF%/100).Limitations
- These equations predict average composition from height, weight and sex in their source cohorts; they do not directly measure your tissues.
- Error can increase for very muscular builds, extreme body sizes, pregnancy, people under 18 and some clinical situations.
- Lean body mass must not be interpreted as muscle mass or used on its own for medical decisions or medication dosing.
Was this tool useful?
How does this tool work?
Lean body mass is the part of body weight not attributed to fat mass. It includes muscle, but also water, bone, organs, blood and other tissues. This calculator compares three established height-and-weight equations so that a single estimate is not presented as an exact measurement.
Choose the sex used by the equations, then enter height and weight. Metric, imperial and stones inputs are converted to the kilograms and centimetres required by the formulas.
Boer supplies the headline figure. James and Hume are calculated from the same profile and shown separately; the range between all three gives a practical view of model variability.
If you already know body-fat percentage, the optional field also calculates lean mass as weight × (1 − body-fat percentage). It stays separate because its reliability depends on how that percentage was obtained.
How to use this tool
Choose the formula sex
All three equations use separate female and male coefficients.
Enter height and weight
Choose your unit system; conversions happen automatically.
Compare the methods
Read Boer as the tool reference, then review James, Hume and the body-fat-derived value when supplied.
Use cases
Track body composition
Use one method consistently over time to follow a trend without treating lean mass as muscle mass.
Use a known body-fat percentage
Convert an existing measured or estimated percentage into lean mass and compare it with Boer.
Tips and best practices
- For tracking, weigh yourself under similar conditions and keep the same method so trends matter more than isolated numbers.
- A gap between Boer, James and Hume is expected because the equations came from different populations and methods.
- If body-fat percentage comes from a smart scale, skinfolds or tape measurements, include the uncertainty of that method in your interpretation.
Frequently asked questions
Is lean body mass the same as muscle mass?
No. Muscle is only one component of lean body mass. Lean mass also includes body water, bone, organs, blood and other non-fat tissues.
Why is Boer the primary formula?
Boer (1984) is newer than Hume (1966) and James (1976) and is a frequently used anthropometric reference. The tool still shows all three because no height-and-weight equation directly measures body composition.
Why do the formulas disagree?
They were derived at different times, from different populations and with different mathematical models. A difference is therefore expected and helps prevent overconfidence in one number.
Is the optional body-fat method more accurate?
The arithmetic is direct, but accuracy depends entirely on the percentage entered. An uncertain body-fat estimate produces an equally uncertain lean-mass result.
Can I use this result for medication dosing?
No. This consumer calculator is not a substitute for a clinician-validated measurement or dosing method.
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