Lean Body Mass
Estimate your lean body mass (fat-free) and fat mass, using the Boer formula.
kg
cm
Lean body mass58.1 kg
Fat mass17.0 kg
How it works
Lean body mass is everything you are made of except fat — muscle, bone, organs and water. Knowing it helps set protein needs, medication doses and realistic body-composition goals.
This calculator uses established formulas such as Boer, which combines your weight, height and sex. For a man of 80 kg and 180 cm it estimates a lean mass of roughly 64 kg, implying about 16 kg of fat. The difference from your total weight is your fat mass.
Unlike total weight, lean mass tends to hold steady or rise with strength training while fat falls, so tracking it shows whether a diet is preserving muscle rather than burning it.
Frequently asked questions
How is lean body mass different from body fat?
They are two parts of the same whole: total weight = lean mass + fat mass. If you know your body-fat percentage, lean mass is simply the rest of your weight.
Why does lean mass matter for a diet?
A good weight-loss plan sheds fat while keeping muscle. Tracking lean mass, not just the scale, tells you whether the weight coming off is fat (good) or muscle (to be avoided).
Is it the same as muscle mass?
No, lean mass includes more than muscle.