Calculation Results
About This Calculator
Calculate Lean Body Mass (LBM), fat mass, body fat percentage, and Fat-Free Mass Index (FFMI) comparing the Boer, James, and Hume clinical formulas.
Frequently Asked Questions
What is Lean Body Mass (LBM)?
Lean Body Mass consists of everything in your body that is not adipose fat tissue, including skeletal muscle, bones, vital organs, blood, connective tissues, and intra-cellular water.
Why is Lean Body Mass critical for clinical medication dosing?
Lipophilic medications distribute into body fat, whereas hydrophilic medications distribute primarily into lean tissue and total body water. Dosing critical drugs (e.g. anesthetic agents, antibiotics, chemotherapy) by total body weight in obese individuals leads to severe toxic overdose.
What does Fat-Free Mass Index (FFMI) measure?
FFMI normalizes lean muscle mass relative to height. An FFMI of 18-20 represents an average person, 21-22 represents an athletic individual, and 25 is recognized as the upper threshold of drug-free natural genetic muscular development.
Which formula is preferred: Boer, James, or Hume?
The Boer formula is the most widely cited and recommended equation in modern medical pharmacology and anesthesia literature for estimating fat-free mass across both normal weight and obese patients.