Lean Body Mass Calculator
Determine your exact Fat-Free Mass (FFM) and Lean Body Mass (LBM) using three established clinical equations: Boer (1984), James (1976), and Hume (1966). These formulas estimate skeletal muscle, bone, and organ mass without skinfold calipers or radiographic imaging.
Formulas apply sex-specific anthropometric regression constants
Current scale weight in kilograms
Standing barefoot height in centimetres
Mean lean tissue mass across Boer, James, and Hume models
How to Use This Calculator
- Select your biological sex.
- Enter your accurate morning barefoot weight in kilograms.
- Input your standing height in centimetres.
- Review your consensus Lean Body Mass and estimated adipose fat weight.
Formula & Calculation Methodology
Lean body mass models estimate the mass of all non-adipose tissues (skeletal muscle, internal organs, bone mineral density, and extracellular water). The Boer formula remains the recognized standard in critical care pharmacology.
Worked Example
A male weighing 75 kg with height 178 cm
Frequently Asked Questions
What constitutes lean body mass?↓
Lean Body Mass (LBM) includes all components of the human body except storage fat. It encompasses skeletal muscles, internal organs (heart, liver, kidneys, brain), skin, bone tissue, and cellular and extracellular water.
Why is Lean Body Mass used in sports nutrition and strength training?↓
Basal metabolic rate and protein requirements correlate far more closely with lean body mass than with total scale weight. Basing protein and carbohydrate intake on lean mass ensures muscular recovery without overfeeding excess fat stores.
Why does the James formula sometimes produce paradoxical drops at extreme obesity?↓
The James equation includes a squared (Weight / Height) term. At extreme BMIs (> 42), this quadratic negative component can mathematically overpower the linear weight term, making the Boer formula vastly preferable for obese individuals.
How does hydration state impact lean body mass measurements?↓
Because water represents approximately 73% of muscle tissue by weight, severe dehydration temporarily depresses measured lean body mass, while acute creatine supplementation or carbohydrate loading temporarily increases it through intracellular water retention.
What limitation should I keep in mind regarding mathematical LBM formulas?↓
Mathematical formulas are statistical approximations based on height and weight. They cannot identify hyper-muscular natural strength athletes whose actual lean mass significantly exceeds standard population regressions. Dual-energy X-ray absorptiometry (DEXA) provides direct tissue confirmation.
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Open calculator →Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.