Lean Body Mass Calculator
Calculate estimated lean body mass and fat mass from bodyweight and body-fat percentage. Results update as you change an input.
Result
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Enter your details to calculate.
What is lean body mass?
Lean body mass is total mass minus fat mass. It includes muscle, bone, organs, connective tissue, and body water.
Lean body mass vs muscle mass
Lean body mass is not the same as skeletal muscle mass because it includes every non-fat component of the body.
How lean body mass is calculated
Fat mass equals bodyweight multiplied by body-fat percentage. Lean body mass equals bodyweight minus that estimated fat mass.
Why lean body mass is useful
Estimated lean mass can add context to body-composition trends, FFMI, and some nutrition planning.
Limitations of body-fat estimates
The result is only as accurate as the body-fat input. Tape measurements, scales, calipers, and scans each have measurement error.
Method note: This is a direct two-compartment calculation; uncertainty comes primarily from the entered body-fat estimate.