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Lean Body Mass Calculator
Lean body mass is everything in your body that is not fat: muscle, bone, organs and water. Enter your sex, height and weight to estimate it with the Boer formula, with the Hume and James formulas alongside so you can see how far they agree.
- Lean share of body weight
- 75.3%
- Implied body fat
- 24.7%
- Hume formula
- 126.9 lb
- James formula
- 138.5 lb
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Formula
How to use it
- Select your sex.
- Enter your height and weight.
- Read your estimated lean body mass, its share of your weight and the body fat that implies.
Worked examples
A man 5 ft 10 in and 180 lb
- Lean body mass (Boer)
- 135.6 lb
- Implied body fat
- 24.7%
- Hume formula
- 126.9 lb
- James formula
- 138.5 lb
A woman 165 cm and 65 kg
- Lean body mass (Boer)
- 101.7 lb
- Implied body fat
- 29%
- Hume formula
- 99 lb
- James formula
- 102.7 lb
What the formulas can and cannot do
These equations predict lean mass from height and weight alone, so they give the average for someone of your size. They cannot see whether you are more or less muscular than that average. If you have a body fat measurement, lean mass = weight × (1 − body fat %) is more personal.
The James formula is known to break down at high body weights, where its result starts to fall as weight rises; Boer is generally preferred for that reason. Lean body mass is sometimes used to scale drug doses, which is a clinical judgement and not something to do from this page.
This is an estimate for general information, not medical advice. Talk to a doctor or other qualified clinician before making health decisions based on it.
Questions people ask
What is the lean body mass of a 180 lb man who is 5 ft 10 in?
About 135.6 lb (61.5 kg) by the Boer formula, which is roughly 75% of body weight and implies about 25% body fat.
Is lean body mass the same as muscle mass?
No. Lean body mass includes bone, organs, skin and body water as well as muscle. Skeletal muscle is typically well under half of total body weight.
What is a normal lean body mass percentage?
Lean mass is commonly around 75–85% of body weight for men and 65–80% for women, the remainder being fat.