Lean body mass calculator

How to calculate lean body mass

1. Choose your sex (male or female).
2. Select metric (kg, cm) or imperial (lbs, ft/in) units.
3. Enter your weight and height.
4. Your lean body mass, fat mass, and body fat percentage appear instantly.

Common uses

• Getting a quick lean mass and fat mass split when you only know your height and weight
• Cross-checking the estimate against a tape-measure reading from the Navy body fat method, which responds to changes in your waist and neck
• Working out nutrition targets set per kilogram of lean mass, next to a daily calorie estimate

Technical specification

• Algorithm or formula: Boer (1984) formula. Men: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. Women: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3. Published in the American Journal of Physiology, volume 247 (1984).
• Browser API or library: Pure JavaScript arithmetic. No external library.
• Input limits: Numeric weight (up to 650 kg) and height 50 to 272 cm (1 ft 8 in to 8 ft 11 in, with inches below 12). Imperial values convert to metric internally. A height outside this range, or a lean mass from the formula that is not between zero and your body weight, shows a hint instead of a result.
• Output: Lean body mass (kg or lbs), fat mass, and implied body fat percentage = (total − LBM) / total.
• Known limitations: A prediction formula, not a measurement. Margin of error is generally a few percent versus DEXA, with poorer accuracy at extreme body compositions. Because the only inputs are weight, height, and sex, the estimate moves only when your weight moves and cannot separate muscle gain from fat gain.

Frequently asked questions

What is lean body mass?

Lean body mass (LBM) is your body weight minus your body fat: muscle, bone, organs, skin, and water. This calculator estimates it from weight, height, and sex with the Boer (1984) formula, so a man 180 cm tall weighing 80 kg gets about 61.4 kg of lean mass and an implied body fat of 23.2%. Results are estimates for informational purposes only.

What is the Boer formula?

The Boer (1984) formula estimates lean body mass from weight and height. For men: LBM = 0.407 × weight (kg) + 0.267 × height (cm) − 19.2. For women: LBM = 0.252 × weight (kg) + 0.473 × height (cm) − 48.3. It was published by P. Boer in the American Journal of Physiology, volume 247 (1984).

How is lean body mass different from total weight?

Total weight includes both lean mass and fat mass. Lean body mass is the portion that is not fat, covering muscle, bone, organs, and water. Two people with the same total weight can have very different body compositions.

Where does the calculation run?

All calculations run locally in your browser using JavaScript. Our servers are not involved at any point.