Lean Body Mass Calculator

Lean body mass (LBM) is your total body weight minus all fat weight. Knowing your LBM helps you set better nutrition targets, track muscle gain during a cut, and understand your body composition beyond the scale. Our calculator uses three validated formulas to estimate your fat-free mass.

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About This Calculator

Lean body mass (LBM) is your total weight minus body fat. This calculator uses three validated estimation formulas: Boer (1984), James (1976), and Hume (1966). The average of all three provides a more reliable estimate. For the most accurate measurement, consider DEXA scanning or hydrostatic weighing. These formulas are intended for adults and may not be accurate for children or adolescents.

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Frequently Asked Questions

What is lean body mass?

Lean body mass (LBM) is everything in your body that is not fat: muscle, bone, organs, water, and connective tissue. For most men, LBM is 75-85% of total weight. For women, it is typically 65-75%.

Why does lean body mass matter?

LBM determines your basal metabolic rate more accurately than total weight. It is also essential for calculating protein needs (many recommendations are based on grams per kg of lean mass) and tracking whether weight changes are from fat or muscle.

Which lean body mass formula is most accurate?

The Boer formula is generally considered the most accurate for adults. However, all estimation formulas have limitations. For the most precise measurement, DEXA scanning or hydrostatic weighing are the gold standard.

How can I increase my lean body mass?

Resistance training (lifting weights) combined with adequate protein intake (1.6-2.2g per kg of body weight) and a slight caloric surplus is the most effective strategy. Progressive overload and consistency are key.

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