Lean Body Mass Calculator
Calculate your lean body mass (LBM) and fat mass from weight, height and sex using the Boer formula. Useful for fitness, dosing and nutrition. Free, private, instant.
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Separate lean mass from fat mass
Your weight is the sum of lean tissue, muscle, bone, organs, water, and fat. Lean body mass is everything that is not fat, and knowing it is more useful than weight alone for tracking fitness. This calculator estimates lean body mass and fat mass from your weight, height and sex using the Boer and related formulas.
Why lean mass is the better tracking number
When you get fitter, your weight may barely move even as fat falls and muscle rises, because the two changes offset. Tracking lean mass separately reveals that progress, which the scale hides. It also matters clinically, since some medication doses are based on lean mass rather than total weight, because fat tissue does not metabolise drugs the way lean tissue does.
An estimate from established formulas
These are estimates from a standard formula for general information, not medical advice. Individual health depends on far more than any single number, so treat the result as a rough guide and consult a professional for anything that matters. The calculation runs entirely in your browser, so your figures are not uploaded.
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Frequently Asked Questions
What is lean body mass?
Everything in your body that is not fat: muscle, bone, organs and water. Fat mass is the remainder, and the two together make up your weight.
Why track lean mass instead of weight?
Because getting fitter can leave your weight unchanged as fat falls and muscle rises. Lean mass reveals that progress, which the scale alone hides.
How is it estimated?
From weight, height and sex using the Boer and related formulas, which correlate those measurements with lean tissue. It is an estimate, not a direct measurement.
Why does it matter clinically?
Some medication doses are based on lean mass rather than total weight, because fat tissue metabolises drugs differently, so the distinction affects dosing.
Is this medical advice?
No. It is a general estimate. Consult a professional for an accurate assessment.
Privacy & Security
All processing happens locally in your browser — nothing is uploaded.
How to Use
Enter your sex, weight and height to estimate lean body mass and fat mass.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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