Lean Body Mass Calculator – LBM and Fat Mass
Calculate lean body mass and fat mass from your weight and body fat percentage. See how much of your weight is muscle, bone and organs versus fat.
Lean Body Mass Calculator
Calculate lean body mass (LBM) from total weight and body fat percentage.
How the lean body mass calculator works
Fat mass = weight × (body fat % ÷ 100). Lean body mass = weight − fat mass. Results are in kg and lb. You need a body fat estimate from calipers, scales or our body fat calculator.
Why lean body mass matters
Total weight does not distinguish muscle from fat. Two people can weigh the same but have very different body composition. Lean body mass (LBM) is everything except fat: muscle, bone, organs, water. A higher LBM at a given weight usually means better metabolic health, strength and function.
To calculate LBM, you need your body fat percentage. Get it from calipers, a body fat scale, or our body fat calculator (Navy method using waist, neck and hip measurements). Then: fat mass = weight × (body fat % ÷ 100), and LBM = weight − fat mass.
Use LBM to track changes over time. When losing weight, the goal is often to lose fat while preserving or gaining muscle. If LBM drops sharply, you may be losing muscle. When gaining, aim to increase LBM. Pair this with our protein intake calculator to support muscle maintenance and growth.