Lean Body Mass Calculator
Estimate how much of your body weight is lean mass versus fat using the Boer formula.
How to use the lean body mass calculator
- Choose units and your sex.
- Enter your weight and height.
- Click Calculate to see lean mass, fat mass and body-fat estimate.
Why lean mass matters
Lean mass drives your metabolic rate and strength potential, and many supplement and protein recommendations are scaled to it rather than total body weight.
Why lean body mass matters
Lean body mass is everything that is not fat: muscle, bone, organs, and water. Tracking it alongside total weight tells you whether a diet is costing you muscle or a training block is building it, which the scale alone can never reveal.
Using LBM to set protein and calories
Many nutrition targets are better set from lean mass than total weight, especially for people with higher body fat. Calculating protein needs per kilogram of lean mass, for example, avoids overestimating requirements. This tool uses the Boer formula, a reliable height-and-weight estimate.
Frequently asked questions
What is lean body mass?
Lean body mass is everything in your body that is not fat — muscle, bone, organs and water. It is a key reference for protein needs and dosing.
How accurate is the Boer formula?
It gives a solid estimate from height and weight alone, though a measured body-fat percentage (with our body-fat calculator) gives a more individualised figure.
How is lean body mass estimated?
From your height, weight, and sex using validated formulas such as Boer. For a direct measurement, methods like DEXA or hydrostatic weighing are more precise.
Should I set my protein by lean mass or total weight?
For lean individuals it makes little difference; for those with higher body fat, basing protein on lean mass avoids overestimating needs.
Can I gain lean mass and lose fat at once?
Yes, especially for beginners, those returning from a break, or people with higher body fat. It is slower than doing either alone but very achievable.
Related tools
Body Fat Calculator
Estimate your body-fat percentage using the U.S. Navy circumference method — just a tape measure required.
FFMI Calculator
Measure your muscularity with the Fat-Free Mass Index, normalised for height.
Protein Intake Calculator
Find your daily protein target based on your body weight and training goal.