Lean Body Mass Calculator
Calculate your lean body mass (LBM) — your weight minus body fat. Used for setting protein targets, calorie needs, and tracking body composition progress.
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How to use this calculator
If body fat % is unknown, the Boer formula estimates LBM from height and weight: LBM = 0.407W + 0.267H − 19.2 (men); 0.252W + 0.473H − 48.3 (women).
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Enter your body weight, height, and sex.
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If you know your body fat percentage (from DEXA, calipers, or smart scales), enter it for a precise result.
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Leave body fat at 0 to use the Boer estimation formula from height and weight.
Frequently asked questions
What is lean body mass?
Lean body mass (LBM) is total body weight minus fat mass. It includes muscle, bone, water, and organs. It is also called fat-free mass (FFM). LBM is the biologically active portion of your body that sets your metabolic rate.
Why use LBM for protein targets?
Setting protein intake relative to LBM (rather than total weight) is more accurate because fat tissue needs very little protein. The general recommendation for active people is 1.6–2.2 g of protein per kg of LBM per day.
How can I measure body fat accurately?
DEXA scanning is the most accurate (±1–2%). Hydrostatic weighing and air displacement plethysmography are also very accurate. Consumer bioelectrical impedance (smart scales) is convenient but can vary by 5–10%. Skinfold calipers with a trained measurer are reasonably accurate.
Lean Body Mass Calculator — LBM, Fat Mass & Protein Targets
Lean body mass and metabolic rate
Your resting metabolic rate (RMR) is driven primarily by lean body mass — muscle and organ tissue are metabolically expensive to maintain. Two people with the same total weight but different LBM will have significantly different calorie needs. This is why body composition, not just the scale number, determines how many calories you need.
Tracking body composition over time
The scale alone is misleading during body recomposition (building muscle while losing fat). Tracking LBM alongside weight tells a much richer story. For example, if you lose 2 kg total weight but LBM stays constant, you know you have lost 2 kg of fat — a better outcome than losing 2 kg of muscle.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →