Lean Body Mass Calculator
Calculates your lean body mass — the weight of everything except body fat — using your choice of three validated clinical formulas. Useful for setting protein targets, dosing medications by lean mass, or tracking body composition changes over time.
About this calculator
Lean Body Mass (LBM) is total body weight minus fat mass and is a key metric in nutrition, pharmacology, and fitness. This calculator supports three peer-reviewed formulas. The Boer formula (generally most accurate) uses: LBM (kg) = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2 for males, and 0.252 × weight(kg) + 0.473 × height(cm) − 48.3 for females. The James formula applies: LBM (kg) = 1.1 × weight(kg) − 128 × (weight(kg) / height(m))² for males, and 1.07 × weight(kg) − 148 × (weight(kg) / height(m))² for females. The Hume formula uses: LBM (kg) = 0.3281 × weight(kg) + 0.3393 × height(cm) − 29.5336 for males, and 0.2957 × weight(kg) + 0.4182 × height(cm) − 43.2933 for females. All results are converted back to pounds for display.
How to use
Example: a 180-lb (81.6 kg), 5′10″ (177.8 cm) male using the Boer formula. Step 1 — convert units: 180 lbs ÷ 2.205 = 81.6 kg; 70 inches × 2.54 = 177.8 cm. Step 2 — apply Boer male formula: LBM = 0.407 × 81.6 + 0.267 × 177.8 − 19.2 = 33.2 + 47.5 − 19.2 = 61.5 kg. Step 3 — convert back to lbs: 61.5 × 2.205 ≈ 135.6 lbs. This means roughly 135.6 lbs is lean tissue, and about 44.4 lbs (24.7%) is fat mass.
Frequently asked questions
What is lean body mass and why is it important to calculate?
Lean body mass is the combined weight of your muscles, bones, organs, connective tissue, and water — everything that is not stored fat. It matters because metabolic rate, athletic performance, and nutrient needs scale closely with LBM rather than total body weight. Clinicians also use LBM to calculate appropriate drug dosages, since fat tissue does not absorb many medications the same way lean tissue does. Tracking LBM over time tells you whether you are losing fat, muscle, or both.
What is the difference between the Boer, James, and Hume lean body mass formulas?
All three formulas estimate LBM from weight and height but were derived from different study populations and methods. The Boer formula (1984) is often recommended for general use and tends to perform well across a broad BMI range. The James formula (1976) is the oldest and can underestimate LBM in obese individuals because its correction term grows sharply with weight. The Hume formula (1966) was derived from cadaver studies and is considered reliable for normal-weight adults. Choosing the formula that matches your population or clinical context improves accuracy.
How can I use lean body mass to set my daily protein intake?
Many sports nutrition guidelines recommend 0.7–1.0 g of protein per pound of lean body mass per day for individuals trying to maintain or build muscle. Using LBM rather than total body weight prevents over-estimating protein needs in higher-body-fat individuals, where a portion of total weight is metabolically inactive fat. For example, someone with 135 lbs of LBM would target roughly 95–135 g of protein daily. Spreading that protein across 3–5 meals maximizes muscle protein synthesis throughout the day.