What this calculator measures
Lean body mass (LBM) is everything in your body that isn't fat — muscle, bone, organs, water, and connective tissue. Tracking LBM alongside total weight gives a much more accurate picture of training outcomes: a successful recomposition phase may show stable scale weight but a clear increase in LBM.
How this calculator works
Lean body mass = body weight × (1 − body fat% ÷ 100). This simple formula requires a reliable body fat percentage input — from the body fat calculator (Navy method) or another measurement source. The accuracy of the LBM figure depends directly on the accuracy of your body fat input.
How to use your result
Track LBM over time rather than at a single point. Losing body weight is only positive if LBM is being maintained or increased. If LBM drops alongside total weight, it signals insufficient protein, excessive deficit, or inadequate training stimulus. Combine with the protein calculator to ensure your intake supports muscle retention.
Important limitation
Calculator results are estimates. Pregnancy, eating disorders, medical conditions, injuries, or concerning symptoms require qualified professional guidance.