Lean Body Mass Calculator
Total weight minus estimated fat mass. The number most metabolic interventions should actually target.
Your details
Use the Body Fat % Estimator if you don't know your body fat percentage.
What this means
What to consider
Medications that may affect your result
Anabolic steroids increase lean muscle mass beyond natural limits, which inflates LBM readings. If you are using testosterone replacement or anabolic compounds, your lean mass reflects both natural and pharmacologically-driven tissue.
Corticosteroids (prednisone, dexamethasone) cause muscle wasting and fat redistribution. This can reduce LBM while increasing fat mass, even if total weight stays stable.
Your baseline may differ from the general population. Discuss with your healthcare provider.
About this tool
Formula
Lean Body Mass = Weight × (1 − Body Fat% / 100). Fat Mass = Weight × (Body Fat% / 100).
Interpretation
LBM includes muscle, bone, organs, and water — everything except stored fat. There are no universal clinical thresholds for LBM because healthy values vary significantly by sex, age, height, and activity level. The value is most useful as a personal baseline to track over time.
Limitations
Accuracy depends entirely on the Body Fat % input. If your body fat estimate has a ±3–4% margin of error, your LBM result carries that same margin. LBM does not distinguish between muscle mass and other lean tissue (bone, organs, water). Dehydration or fluid retention can shift LBM without reflecting actual muscle change.
Sources
ACSM Guidelines for Exercise Testing and Prescription. Body composition assessment methodology review, Heymsfield et al. (2014).
Educational tool only. Not for diagnostic purposes. Consult a healthcare provider for medical decisions.