Lean Body Mass Calculator
An 80 kg man at 180 cm has about 61.4 kg of lean body mass with the Boer formula used here. This lean body mass calculator estimates lean mass and fat mass from your weight and height using the sex-specific Boer formula. Enter your sex, weight in kilograms, and height in centimeters to see estimated lean body mass, fat mass, and fat mass as a percentage of total weight.
Quick answer
Lean body mass is your estimated weight minus estimated fat mass.
What this tells you
- •Lean body mass is your estimated weight minus estimated fat mass.
- •The Boer formula uses different constants for men and women.
- •It only needs weight and height, so it skips body fat percentage as an input.
- •The result is a population-based estimate, not a body scan or a diagnosis.
How to Use
- 1Select male or female so the calculator applies the matching Boer formula.
- 2Enter your current body weight in kilograms.
- 3Enter your current height in centimeters.
- 4Calculate to see estimated lean body mass, fat mass, and fat mass percentage.
- 5Track the trend over weeks alongside consistent weigh-ins rather than judging a single result.
How It Works
Formula
Male: LBM = 0.407 x weight(kg) + 0.267 x height(cm) - 19.2
Female: LBM = 0.252 x weight(kg) + 0.473 x height(cm) - 48.3
Fat mass = weight - LBMThe Boer formula estimates lean body mass directly from weight and height using sex-specific constants, without needing a body fat percentage as an input. Fat mass is simply total weight minus the estimated lean body mass, and fat mass percentage divides that fat mass by total weight. This formula was built from population data and gives a reasonable estimate for most adults, but it is still an approximation rather than a direct measurement.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Male at 80 kg and 180 cm
The male Boer formula gives 0.407 x 80 + 0.267 x 180 - 19.2, which rounds to 61.4 kg of lean body mass. Fat mass is 80 minus 61.4, or 18.6 kg, which is about 23.2% of total weight.
Female at 65 kg and 165 cm
The female Boer formula gives 0.252 x 65 + 0.473 x 165 - 48.3, which rounds to 46.1 kg of lean body mass. Fat mass is 65 minus 46.1, or 18.9 kg, which is about 29.0% of total weight.
Common mistakes
- Entering pounds as kilograms or inches as centimeters
- Selecting the wrong sex option, which changes the formula constants and the result
- Treating one lean body mass estimate as a precise or medical measurement
- Comparing results with tools that use a different formula, such as the Boer, James, or Hume methods
Limitations
This lean body mass calculator uses the Boer formula, which estimates lean mass from weight and height alone and does not account for body frame, muscle distribution, hydration, age, ethnicity, or pregnancy. It assumes adult body proportions similar to the population used to build the formula, so results may be less accurate for very muscular people, very lean people, older adults, and children. Treat every result as a general estimate, not a substitute for a body composition scan such as DEXA or BIA.