Lean Body Mass Calculator
Estimate your lean mass and fat mass with the Boer formula.
Separate muscle from fat
Lean body mass is your total weight minus fat — the muscle, bone, organs, and water that make up the rest. The Boer formula estimates it from weight, height, and sex without needing a body scan.
An 80 kg, 180 cm man has a lean mass around 61 kg by this formula, leaving roughly 19 kg of fat. Tracking lean mass while dieting helps confirm you are losing fat rather than muscle.
Useful and private
It applies the Boer equation in your browser, so your measurements never leave your device.
Frequently Asked Questions
What is lean body mass?
Everything in your body that is not fat — muscle, bone, organs, and water. The Boer formula estimates it from weight, height, and sex.
Why track it?
Lean mass is what you want to keep or grow while losing fat. It is also used to scale certain medication doses.
How accurate is it?
It is a solid estimate for average builds. Very muscular or very lean people may read a little off, since it is based on population averages.
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