Lean Body Mass Calculator

Calculate your lean body mass with the Boer, James and Hume formulas.

Units

Sex

Height

Height (feet)

Inches

Weight

Enter your values to see the result.

These results are estimates for general information, not medical advice. Body shape, muscle mass, age, ethnicity and health conditions all affect what is right for you, so talk to a doctor or dietitian before making health decisions.

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How this calculation works

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Formula: Boer lean mass (kg): men 0.407W + 0.267H − 19.2; women 0.252W + 0.473H − 48.3. W is weight in kg and H is height in cm. James and Hume estimates are displayed for comparison.
Variables: Units: Metric, Imperial
Sex: Male, Female
Height
Height (feet)
Inches
Weight
Weight
Units: Height: cm
Height (feet): ft
Inches: in
Weight: kg
Weight: lb
Example: A man who is 175 cm tall and weighs 70 kg has a lean body mass of about 56 kg with the Boer formula, meaning roughly 14 kg (20%) of his weight is fat.
Assumptions: These results are estimates for general information, not medical advice. Body shape, muscle mass, age, ethnicity and health conditions all affect what is right for you, so talk to a doctor or dietitian before making health decisions.
Source: ToolzHive calculation guide and calculator implementation. External reference verification is pending.
Last reviewed: Review date not yet recorded.

Methodology & References

The method depends on the selected model and input options. Review the assumptions and references above before interpreting the result.

Choose metric or imperial units and select your sex.
Enter your height and weight.
Compare the lean body mass from each formula. The Boer formula is shown first because it is generally the most accurate.

Interpretation and limitations

Which lean body mass formula is best? Studies generally find the Boer formula the most accurate of the three for adults. The James formula can give unrealistic results at very high body weights.
How can I measure lean body mass directly? DEXA scans, bioelectrical impedance scales and hydrostatic weighing measure body composition directly. A tape-measure body fat estimate is a good free alternative.
Why does lean body mass matter? Muscle burns more energy than fat and supports strength, balance and metabolic health. Keeping lean mass while losing fat is the goal of most healthy weight-loss plans.

References

External reference verification is pending. The formula and examples describe the current ToolzHive implementation.

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How to use the Lean Body Mass Calculator

Lean body mass (LBM) is everything in your body except fat: muscles, bones, organs, skin and water. This calculator estimates it from your height, weight and sex with three published formulas, Boer, James and Hume, and shows the body fat percentage each implies. Knowing your lean mass helps with protein targets, the Katch–McArdle BMR formula and tracking muscle as you train.

1 Choose metric or imperial units and select your sex.
2 Enter your height and weight.
3 Compare the lean body mass from each formula. The Boer formula is shown first because it is generally the most accurate.

Example and practical tips

A man who is 175 cm tall and weighs 70 kg has a lean body mass of about 56 kg with the Boer formula, meaning roughly 14 kg (20%) of his weight is fat.

Frequently asked questions

Which lean body mass formula is best?

Studies generally find the Boer formula the most accurate of the three for adults. The James formula can give unrealistic results at very high body weights.

How can I measure lean body mass directly?

DEXA scans, bioelectrical impedance scales and hydrostatic weighing measure body composition directly. A tape-measure body fat estimate is a good free alternative.

Why does lean body mass matter?

Muscle burns more energy than fat and supports strength, balance and metabolic health. Keeping lean mass while losing fat is the goal of most healthy weight-loss plans.

How to Use Lean Body Mass Calculator
Calculate your lean body mass (weight without fat) using the Boer, James and Hume formulas, and see your estimated body fat percentage. Free LBM calculator.