Lean Body Mass Calculator

Calculate your lean body mass — everything in your body that is not fat, including muscle, bones, organs, and water.

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How It Works

Lean Body Mass (LBM) is your total body weight minus your fat mass. It includes muscle, bones, organs, skin, blood, and water. Knowing your LBM is important because it drives your caloric needs more than total weight does — muscle tissue burns more calories at rest than fat tissue. The Boer formula (1984) and Hume formula (1966) estimate LBM from height and weight alone. If you know your body fat percentage (from calipers, a DEXA scan, or the Navy method), the direct calculation (weight times 1 minus body fat fraction) is more accurate. Tracking LBM over time helps you confirm whether you are gaining muscle during a bulk or preserving muscle during a cut.