Free Body Composition Calculator - Analyze Your Body Metrics
Analyze your body composition metrics including muscle mass, fat percentage, and lean body mass.
Formula & Methodology
The Body Composition Calculator uses your body-fat percentage (from a separate measurement) and your total weight to split your mass into two parts: fat mass (weight times body-fat percentage) and lean body mass (weight minus fat mass). Lean body mass includes muscle, bone, organs, and water.
- Body Fat Mass = Weight × Body Fat %
- Lean Body Mass = Weight − Body Fat Mass
Worked Example
Using the Body Composition Calculator: apply the formula above to your input values. For instance, Body Fat Mass = Weight × Body Fat %, then Lean Body Mass = Weight − Body Fat Mass. The tool performs each step instantly and shows the result.
Frequently Asked Questions
What does body composition mean?
It is the proportion of fat mass versus lean mass (muscle, bone, water) in your body, a better health signal than weight alone.
Why track body fat instead of just weight?
Two people at the same weight can have very different fat and muscle levels, and composition better reflects fitness and health risk.
How accurate are these estimates?
Formula-based estimates give a useful trend but are less precise than DEXA or hydrostatic testing, so watch the direction over time.