Lean Body Mass Calculator
Estimate lean body mass from height, weight, and sex.
A lean body mass (LBM) calculator estimates the weight of everything in your body except fat - muscle, bone, organs, and water - using the Boer formula, one of the most commonly referenced equations for estimating fat-free mass from height, weight, and sex. Lean body mass is often used alongside body fat percentage to get a fuller picture of body composition than weight or BMI alone provide.
Enter your height, weight, and sex to calculate your estimated lean body mass.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Male, 85 kg, 178 cm | LBM ≈ 62.9 kg | Boer formula (men): LBM = 0.407(85) + 0.267(178) − 19.2 = 34.6 + 47.5 − 19.2 ≈ 62.9 kg. |
| Female, 60 kg, 165 cm | LBM ≈ 44.9 kg | Boer formula (women): LBM = 0.252(60) + 0.473(165) − 48.3 = 15.1 + 78.0 − 48.3 ≈ 44.9 kg. |
Why Lean Body Mass Matters Beyond the Scale
Two people can weigh the same amount but have very different body compositions - one with more muscle and less fat, another with less muscle and more fat. Lean body mass helps separate these cases, which matters for tracking fitness progress: someone gaining muscle while losing fat might see very little change on a bathroom scale, even though their body composition is meaningfully improving.
The Boer Formula and Its Alternatives
The Boer formula, developed in 1984, is one of several established equations for estimating lean body mass, alongside alternatives like the James and Hume formulas, each using slightly different coefficients derived from different reference populations. Like BMI and ideal weight formulas, these are population-based estimates rather than direct measurements - a body composition scan (like DEXA) provides a more precise individual measurement than any formula based on height and weight alone.
Using Lean Body Mass for Nutrition and Training Goals
Lean body mass is sometimes used as the basis for protein intake recommendations, since muscle tissue (not fat) is what primarily uses dietary protein for repair and growth - basing protein targets on lean body mass rather than total body weight can be more precise for individuals with a higher or lower than average body fat percentage.
How to Use the Lean Body Mass Calculator
- Open the Lean Body Mass Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the lean body mass calculator works.
Frequently Asked Questions
What is lean body mass?
Lean body mass is your total body weight minus fat mass - it includes muscle, bone, organs, and water. It's often used alongside body fat percentage to assess body composition beyond what weight or BMI alone can show.
How is lean body mass calculated from weight and body fat percentage?
If you know your body fat percentage, lean body mass equals total weight minus (total weight x body fat percentage). This calculator's Boer formula instead estimates lean mass directly from height, weight, and sex when body fat percentage isn't known.
What is the Boer formula?
The Boer formula, developed in 1984, is one of several established equations for estimating lean body mass from height, weight, and sex - it is one of the more commonly referenced formulas alongside similar alternatives like the James and Hume formulas.
Is a formula-based lean body mass estimate as accurate as a body scan?
No. Formula estimates are population-based approximations. A DEXA scan or other direct body composition measurement method provides a more precise individual reading than any height/weight-based formula.
Why would I use lean body mass instead of just tracking weight?
Because weight alone does not distinguish muscle gain from fat loss (or vice versa) - two people at the same weight, or the same person over time, can have very different body compositions that lean body mass helps clarify.
Can I use lean body mass to set my protein intake target?
Yes, some people base protein targets on lean body mass rather than total body weight, since muscle tissue is what primarily uses dietary protein - this can be more precise for individuals with higher or lower than average body fat.
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Last updated: September 27, 2026.