Why does lean body mass matter?

It is a better anchor than total weight for setting protein targets and judging progress, since gaining muscle while losing fat can keep your weight steady while your lean mass rises.

Is this the same as muscle mass?

Not exactly. Lean body mass includes muscle plus bone, organs, and water. Muscle is the part you can build with training, and it is the largest changeable piece of your lean mass.

Verified formulaLast reviewed July 2026

Lean Body Mass Calculator

Estimate how much of your weight is lean tissue rather than fat.

Your details

Weight (lbs)

Height (ft)

Height (in)

Sex

Calculated live in your browser. Nothing is stored or sent anywhere.

Awaiting details

—

Fill in your details to see your result.

A mathematical estimate based on validated equations, for education only. It is not a diagnostic tool.

The science

Lean body mass is everything in your body that is not fat: muscle, bone, organs, and water. Knowing it helps you understand your body composition and set realistic protein and training goals. This calculator uses the Boer formula, a well-regarded estimate based on your height and weight.

The formula

Boer formula, from height and weight

Sources

1
Boer P. Estimated lean body mass as an index for normalization of body fluid volumes (1984).
2
American Council on Exercise body composition guidance

Common questions

This tool is for education only and is not a diagnostic device. Consult a licensed clinician before making health decisions.