Lean Body Mass Calculator
Calculate your lean body mass from weight, height, and sex using the Boer formula.
How to use this tool
- Enter weight, height and sex in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your lean body mass and the full breakdown beneath it.
Lean body mass is your total weight minus fat. The Boer formula uses height and weight to give a quick estimate.
⚠ This tool is for general information and education only and is not medical advice. Consult a qualified healthcare professional before making health decisions.
Formula
For males: LBM (kg) = 0.407 × Weight (kg) + 0.267 × Height (cm) − 19.2
For females: LBM (kg) = 0.252 × Weight (kg) + 0.473 × Height (cm) − 48.3
This is the Boer formula (1984).
How it works
The Boer formula estimates lean body mass — total body weight minus fat mass — from weight and height using sex-specific regression coefficients derived from cadaver analysis and clinical measurements. It is considered more accurate than simpler height-based formulas (such as the James or Hume formulas) for individuals within the normal BMI range.
The formula does not directly measure body fat and cannot account for unusual muscle-to-fat ratios in athletes or individuals with obesity. For greater precision, methods such as DEXA scanning, underwater weighing, or air displacement plethysmography are preferred.
Worked example
- Sex: male. Weight: 70 kg. Height: 175 cm.
- LBM = 0.407 × 70 + 0.267 × 175 − 19.2
- = 28.49 + 46.725 − 19.2
- = 56.015 ≈ 56.02 kg.
Lean Body Mass: 56.02 kg
Common mistakes to avoid
- Entering height in inches instead of centimeters — the Boer formula uses centimeters; a height in inches produces an LBM result that is far too low.
- Selecting the wrong sex — the male and female Boer coefficients differ substantially, and choosing incorrectly shifts LBM by several kilograms.
- Expecting LBM to equal goal body weight — lean body mass includes bones, organs, and water, not just muscle, and is a fixed baseline, not a fitness target.
Key terms
- Lean Body Mass (LBM)
- Total body weight minus adipose (fat) tissue; includes muscle, bone, organs, water, and connective tissue.
- Boer formula
- A 1984 regression equation by Boer that estimates LBM from weight, height, and sex using coefficients derived from clinical body-composition studies.
- Fat-free mass
- Essentially synonymous with lean body mass in most clinical contexts, though strict definitions may differ in whether residual lipids in organs are included.
- DEXA scan
- Dual-energy X-ray absorptiometry — a medical imaging technique that directly measures bone mineral density, fat mass, and lean mass with high accuracy.
- Body composition
- The proportion of fat mass to lean mass in the body; a more informative health metric than total body weight or BMI alone.
Frequently asked questions
- What is lean body mass?
- LBM = total body weight minus body fat weight. It includes muscle, bone, water, and organs. It is used to calibrate protein intake and medication dosing.
- Which formula does this use?
- This calculator uses the Boer formula (1984), which is widely used in clinical settings. The Janmahasatian formula is more accurate but requires additional measurements.