Lean Body Mass (LBM)
Your total weight minus fat — muscle, bone, organs, and water. Used to set protein targets and evaluate composition changes.
Data updated: 2026-08-20 (verified vs primary service regulations)
Formula
LBM = weight (lb) × (1 − body fat %)
Healthy range
Varies widely with frame and training; a 180-lb man at 15% body fat has ~153 lb of lean mass.
Military & first-responder angle
Preserving LBM during ABCP weight loss is the difference between staying strong and getting weak — the reason programs pair calorie targets with strength training.
Calculator
Lean body mass from weight and an estimated body-fat %. Useful for tracking training progress.
Result
About this calculator
Lean body mass is everything that is not fat — muscle, bone, water, and organs — derived from weight and an estimated body-fat %.
The formula
LBM = weight × (1 − body-fat%). Convert to lb or kg as needed.
Frequently asked questions
Q: Why track lean mass?
A: It shows training progress independent of total weight, which moves with water and fat.
Q: How often should I re-estimate?
A: Re-estimate body-fat every few weeks; a single reading drifts with hydration and time of day.
Q: Is LBM the same as muscle?
A: No. LBM includes bone and water; muscle is only part of it.
How to read the result
Lean body mass is everything that is not fat, which includes muscle, bone, water, organs, and connective tissue. That definition matters because the number is derived rather than measured: it comes from subtracting an estimated fat mass from a scale weight, so any error in the fat estimate is inherited by the lean figure. A four point error in body-fat percentage on a two hundred pound person is about eight pounds of lean mass.
Used honestly it is still a useful training signal, because it separates two things a scale conflates. Weight can stay flat while lean mass rises and fat falls, and that recomposition is invisible to a scale on its own. Track the trend across months using one consistent measurement method, and treat any change smaller than the inherent error of that method as noise rather than progress.
Quick answers
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