- Enter your sex, height, and weight. The calculator uses three validated anthropometric formulas (Boer, James, Hume) that estimate LBM from these measurements. All three give slightly different results, and the average provides the best estimate.
- Enter body fat % (optional). If you know your body fat percentage from a DEXA scan, Navy method, or caliper test, the calculator shows LBM directly: LBM = total weight × (1 - BF%). This method is more accurate than the formulas when you have a reliable BF% measurement.
- Use LBM for calorie needs. The Katch-McArdle BMR formula uses LBM instead of total weight, giving a more accurate metabolic rate for both lean and muscular individuals.
Lean Body Mass Calculator
Calculate your lean body mass: the weight of everything in your body except fat.
ft
in
lbs
%
Estimated Lean Body Mass
131.7 lbs
Average of 3 formulas
| Formula | kg | lbs |
|---|---|---|
| Boer | 60.6 | 133.6 |
| James | 61.8 | 136.3 |
| Hume | 56.8 | 125.3 |
| From BF% | 65.1 | 143.5 |
| Average | 59.7 | 131.7 |
How to Calculate Lean Body Mass
Lean Body Mass Formulas
Boer (men): LBM = 0.407W + 0.267H - 19.2 Boer (women): LBM = 0.252W + 0.473H - 48.3 James (men): LBM = 1.1W - 128(W/H)² James (women): LBM = 1.07W - 148(W/H)² Hume (men): LBM = 0.3281W + 0.3393H - 29.5336 Hume (women): LBM = 0.2969W + 0.4169H - 43.2933 W = weight in kg, H = height in cm From BF%: LBM = W × (1 - BF%/100)
Katch-McArdle BMR (uses LBM instead of weight):
BMR = 370 + (21.6 × LBM in kg) Example: LBM = 65 kg BMR = 370 + (21.6 × 65) = 370 + 1,404 = 1,774 cal/day
Frequently Asked Questions
Lean Body Mass (LBM) is your total body weight minus all fat mass. It includes muscle, bone, organs, skin, and body water. For a 180-lb person with 20% body fat, fat mass = 36 lbs and LBM = 144 lbs. LBM is a better fitness indicator than total weight because it separates functional mass from fat. It is used for precise calorie calculations (the Katch-McArdle formula), medication dosing (many drugs are dosed per LBM, not total weight), and tracking body recomposition.
Resistance training and adequate protein intake are the two primary drivers. Progressive overload (gradually increasing weight, reps, or sets over time) signals muscle growth. Protein at 1.6-2.2 g/kg of bodyweight provides the raw material for muscle synthesis. A slight caloric surplus (200-400 calories above maintenance) supports muscle gain while minimizing fat accumulation. Sleep is critical: most muscle repair and growth hormone release occurs during deep sleep.
LBM includes all non-fat tissue: skeletal muscle, smooth muscle, bone, organs, water, and connective tissue. Muscle mass refers specifically to skeletal muscle. For an average adult, skeletal muscle is about 38-42% of total body weight for men and 28-32% for women. LBM is typically 75-80% of total body weight for lean individuals. DEXA scans can differentiate these components precisely, while anthropometric formulas estimate total LBM.
The Boer, James, and Hume formulas estimate LBM from height and weight with average errors of 2-5 kg compared to DEXA scanning. They tend to be less accurate at body weight extremes (very lean athletes or significantly obese individuals). For people who know their body fat percentage from DEXA or a Navy method test, the direct calculation (LBM = weight × (1 - BF%)) is more accurate than any formula.
Yes, this is called "body recomposition." It is most achievable for beginners, detrained individuals returning to exercise, and those with high body fat percentages. In these groups, the body can simultaneously build muscle and lose fat. For advanced trainees at lower body fat levels, true recomposition is very slow. The key requirements: high protein intake (2g/kg+), consistent resistance training, and either a very slight caloric deficit or maintenance calories.
Related Calculators
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Estimate your body fat percentage using body measurements with the US Navy method.
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Ideal Weight Calculator
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