What is a normal lean body mass?

For most adults it's roughly 70 to 90% of body weight for men and 60 to 80% for women.

Is lean body mass the same as muscle?

No. Muscle is only part of it; bones, organs and water make up the rest.

Are these calculators free?

Yes. Every calculator is free with no sign-up. Clearly labeled ads keep it that way.

Calculations run in your browser. Share links put inputs in the URL, which can be read by anyone you send it to and is sent to the hosting server when opened. Avoid sharing sensitive numbers. Currency conversion requests public exchange rates.

How accurate are the results?

Results follow the formulas and assumptions shown, with normal rounding and numerical limits. Taxes, rates and health guidance can change, so treat these as estimates and confirm important decisions with a qualified professional.

Lean Body Mass Calculator

Your weight minus body fat, estimated three ways.

100% Free
Instant Results
No Sign Up

Lean Body Mass Calculator

Lean body mass by Boer, James and Hume

Units

Age

years

Sex

Height

Weight

Lean body mass (Boer)

127.5 lb

80% of your weight; body fat about 20%

Boer (1984)Body fat 20%: 127.5 lb
James (1976)Body fat 19%: 129 lb
Hume (1966)Body fat 25%: 120.4 lb

W = weight in kg, H = height in cm. These are population estimates; a body fat measurement gives a better number (LBM = weight × (1 - body fat %)).

Formula	Men
Boer	0.407W + 0.267H - 19.2
James	1.1W - 128(W/H)²
Hume	0.32810W + 0.33929H - 29.5336

More Fitness & Health Calculators

View all calculators

Every calculator you need.

Free, fast, and easy to use.

Browse all 204 calculators

Calculators: 204+
Free to use: 100%
Results as you type: Instant

How the lean body mass calculator works

Lean body mass is everything that isn't fat: muscle, bone, organs, skin and water. It's used to dose some medicines and to set calorie and protein targets (Katch-McArdle BMR uses it).

The Boer, James and Hume formulas estimate it from height, weight and sex. For children 14 and under the Peters formula is added, which is designed for kids. If you know your body fat percentage, lean mass is simply weight × (1 - body fat).

Using and checking your result

Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.

This tool provides an estimate, not a diagnosis, treatment plan or individualized medical advice. Population formulas may not fit children, pregnancy, athletes or people with health conditions. Discuss health decisions with a qualified clinician.

Share links may contain your input values. Anyone with the URL can read them; avoid sharing sensitive personal or financial information.