What lean body mass means
Lean body mass is everything in your body that is not fat: muscle, bone, organs, connective tissue and the water they hold. Subtracting it from your total weight leaves fat mass, which this tool also reports along with the resulting body-fat percentage.
The estimate uses the Boer formula, a well-regarded equation that predicts lean mass from your weight, height and sex.
Reading the breakdown
The pie chart splits your weight into lean mass and fat mass so you can see the proportion at a glance. This is something BMI cannot show, since BMI only relates weight to height.
Knowing your lean mass is useful for setting protein targets, gauging how much of a weight change is muscle versus fat, and scaling certain nutrition and training goals.
Accuracy and caveats
Formula-based estimates are convenient but have limits:
- They assume an average body composition and can miss outliers.
- Very muscular or very lean people are most likely to be misestimated.
- Hydration shifts can change the numbers from day to day.
- For precision, methods such as DEXA or hydrostatic weighing are needed.
Health note
This is an educational estimate, not a clinical measurement. Use it as a rough guide rather than a diagnosis, and consult a qualified professional before making decisions about diet, training or health.
Formula
Boer — male: 0.407·kg + 0.267·cm − 19.2; female: 0.252·kg + 0.473·cm − 48.3Frequently asked questions
- How is lean body mass different from BMI?
- BMI only relates weight to height. Lean body mass separates fat from non-fat tissue, giving a better picture of body composition.