Lean Body Mass Calculator (Boer Formula)
Lean mass, fat mass and implied body fat percentage from height, weight and sex.
Results
What this tool does
Lean body mass is everything except fat: muscle, bone, organs and water. It is the figure that actually drives resting metabolism and it is what many drug doses are properly scaled to. The Boer formula, published in 1984, is the version most widely used in clinical work, and it needs nothing but height and weight. Enter 1 for men and 0 for women.
Formula
men: 0.407 W + 0.267 H − 19.2 ; women: 0.252 W + 0.473 H − 48.3 (Boer formula)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
sx | Sex | — |
kg | Body weight | kg |
ht | Height | cm |
LM | Lean body mass | kg |
FM | Fat mass | kg |
FP | Body fat | % |
LI | Lean mass index | kg/m² |
Worked example
- Sex1
- Body weight80 kg
- Height178 cm
- Lean body mass60.886 kg
- Fat mass19.114 kg
- Body fat23.89 %
- Lean mass index19.22 kg/m²
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
Frequently asked questions
Why use lean mass rather than total weight?
Because fat is metabolically quiet. Resting energy expenditure, protein requirements and the distribution of many drugs all track lean mass far more closely than they track the number on the scales, which is why anaesthetists and oncologists dose on it. The Boer formula is an estimate from height and weight alone, so it cannot know about an unusual build; measured methods beat it whenever they are available.