Lean Body Mass Calculator
Lean Body Mass (LBM) represents the total weight of your body minus fat mass — including muscles, bones, organs, and water. Knowing your LBM is essential for setting accurate nutrition goals, tracking body composition changes, and understanding your baseline metabolic needs.
This calculator uses the Boer formula (1984), which estimates lean body mass from weight, height, and sex. It also computes your body fat mass and body fat percentage, giving you a complete picture of your body composition.
How it works
Boer Formula — Male: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. Female: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3. Fat Mass = Total Weight − LBM.
Use cases
- Setting protein intake targets based on lean mass
- Tracking body recomposition progress over time
- Estimating resting metabolic rate more accurately than weight alone
- Guiding strength training and nutrition planning
Frequently asked questions
What is lean body mass?
Lean body mass (LBM) is your total body weight minus fat mass. It includes muscles, bones, organs, and body water. LBM is useful for setting nutrition targets and estimating metabolic needs, because lean tissue drives most of your resting energy expenditure.
How is lean body mass calculated with the Boer formula?
The Boer formula (1984) estimates LBM from weight, height, and sex. For men: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. For women: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3. Fat mass is then total weight minus LBM.
What is the difference between lean body mass and muscle mass?
Muscle mass is only one component of lean body mass. LBM also includes bones, organs, connective tissue, and water, so it is always larger than muscle mass alone. An increase in LBM often reflects muscle gain, but changes in hydration can also move the number.
How do I calculate body fat percentage from lean body mass?
First compute fat mass: Fat Mass = Total Weight − LBM. Then divide by total weight and multiply by 100: Body Fat % = (Fat Mass ÷ Total Weight) × 100. For example, a 80 kg person with 60 kg of LBM has 20 kg of fat mass, or 25% body fat.
How accurate is the Boer formula?
The Boer formula is a population-based estimate derived from weight, height, and sex, so it cannot capture individual differences in body composition. Methods like DEXA scans or bioelectrical impedance provide more precise measurements. Use the result as a reference point, and consult a healthcare or nutrition professional before making significant changes based on it.