Lean Body Mass Calculator

Lean body mass is body weight minus stored fat. It includes muscle, bone, organs, connective tissue, and body water, so it is not the same as skeletal muscle mass. Clinicians and researchers use lean mass when a total body weight value could overstate the amount of metabolically active tissue. The estimate can support nutrition planning, medication discussions, fitness tracking, and interpretation of changes in body composition. This calculator uses the adult Boer equations. For males, lean body mass in kilograms equals 0.407 times weight in kilograms plus 0.267 times height in centimeters minus 19.2. For females, it equals 0.252 times weight plus 0.473 times height minus 48.3. Estimated fat mass is total weight minus lean mass, and the displayed body fat percentage is that difference divided by total weight. Keeping every input in the stated metric unit is essential because the coefficients were fitted to kilograms and centimeters. Equation-based lean mass is convenient but remains an estimate. Hydration, age, ethnicity, athletic development, pregnancy, edema, amputation, and body proportions may make an individual differ from the population used to derive the formula. Very short, tall, light, or heavy values may also produce less reliable estimates. Direct techniques such as dual-energy X-ray absorptiometry, air-displacement plethysmography, or a professionally administered bioimpedance assessment can provide more individualized information, although each method has its own assumptions and measurement error. Use repeated estimates under similar conditions when tracking a trend. Weigh at a consistent time, use the same scale, and measure standing height without shoes. A changing result may reflect both actual tissue change and normal shifts in water or glycogen. The number should therefore be interpreted alongside waist circumference, strength, nutrition, symptoms, and clinical goals rather than treated as a diagnosis. This tool is intended for education and general planning, not for selecting a drug dose or diagnosing a health condition. Some medications use specific ideal, adjusted, or measured body-weight rules instead of estimated lean mass. A clinician or pharmacist should confirm the appropriate weight scalar whenever treatment decisions depend on body composition.