Lean Body Mass Calculator

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Calculate your lean body mass and fat mass from height, weight and sex using the Boer formula, or directly from a measured body-fat percentage.

kg
cm
ft
in
%
If known, this is used directly instead of the Boer estimate.
Lean body mass –
Fat mass –
Lean mass % –
Method used –
The Boer formula estimates lean mass from height, weight and sex. Entering a measured body-fat percentage gives a more accurate result.

About Lean Body Mass Calculator

The lean body mass calculator estimates how much of your weight is everything except fat — muscle, bone, organs and water. From your sex, height and weight it applies the Boer formula: 0.407 × weight + 0.267 × height − 19.2 for men, and 0.252 × weight + 0.473 × height − 48.3 for women (kg and cm).

If you already know your body-fat percentage from a scan or smart scale, enter it and the tool uses it directly instead of the Boer estimate — a more accurate route. Either way you get your lean body mass, fat mass and lean-mass percentage, with the method used clearly labeled.

Lean body mass is a better anchor than total weight for protein targets, some medication dosing and tracking muscle gain during a recomposition. The calculator is free, supports metric and imperial units, and runs in your browser.

How to use Lean Body Mass Calculator

  1. Select your sex and preferred units (metric or imperial).
  2. Enter your weight and height.
  3. Optionally enter a measured body-fat percentage for a direct calculation.
  4. Read your lean body mass, fat mass, lean-mass percentage and the method used.

Frequently asked questions

A validated equation that predicts lean body mass from weight, height and sex. It is widely used clinically when no body-composition measurement is available, and it is the default method in this calculator.

Yes. A measured value from a DEXA scan, calipers or a bioimpedance scale lets the tool compute lean mass directly as weight × (1 − body fat %), which beats any formula estimate.

It mirrors body fat: men commonly carry roughly 75–90% lean mass and women 68–85%, varying with age and training. Trends over time matter more than a single reading.

No — lean mass includes bone, organs, skin and body water as well as muscle. Muscle is typically around half of lean mass, so gains in LBM usually, but not exclusively, reflect muscle growth.

They are general estimates: the Boer formula is a population average and even measured body-fat percentages carry error. Use the figures for tracking and planning, not as medical advice.
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