How lean body mass is calculated
Lean body mass is your total weight minus your body fat: muscle, bone, organs and water. This calculator uses the Boer formula, which estimates it from your height, weight and sex. It is useful for setting protein targets, dosing some medications, and tracking whether weight change is muscle or fat.
Worked example
A man 180 cm tall weighing 80 kg has a lean body mass of about 61.4 kg by the Boer formula, meaning roughly 18.6 kg is fat.
Good to know
These formulas use height, weight and sex only, so they are approximations. For a precise figure, a body composition scan such as DEXA measures fat and lean mass directly.
Frequently asked questions
What is lean body mass?
Everything in your body that is not fat: muscle, bone, organs and water. It is your total weight minus your fat mass.
How is it different from BMI?
BMI compares weight to height and cannot separate fat from muscle. Lean body mass estimates the non-fat portion specifically.
How is this different from body fat percent?
Body fat percent is the share of fat; lean body mass is the kilograms of everything else. They are two views of the same thing.
Why does protein depend on lean mass?
Muscle drives protein needs, so many coaches set protein per kilogram of lean mass rather than total weight.
Is the Boer formula accurate?
It is a solid estimate for most adults. For precision, a DEXA or bioimpedance scan measures it directly.