Lean Body Mass Calculator
Calculate your lean body mass (LBM) and estimated body fat percentage using the Boer, James, and Hume formulas.
Your details
Lean body mass (average of 3 formulas)
133.6 lb
Estimated body fat: 24.2%
By formula
Boer (1984)
135.4 lb
James (1976)
138.2 lb
Hume (1966)
127.4 lb
Frequently Asked Questions about the Lean Body Mass Calculator
What is lean body mass and how is it different from body fat?
LBM is your total body weight minus fat mass: muscle, bone, organs, skin, and water. Body fat is everything else. Subtracting LBM from total weight gives an estimated body fat percentage.
Which lean body mass formula is most accurate?
The Boer formula is widely cited as the most reliable for healthy adults. James tends to overestimate in obese individuals. Hume sits between the two. Using the average smooths out individual formula bias.
Why do the three formulas give different results?
Each formula was derived from a different study population (Boer 1984, James 1976, Hume 1966) using different reference methods. They weight body weight and height differently, so estimates can diverge by several kilograms.
When should I use a lean body mass estimate?
Clinicians use LBM to dose certain medications (especially anesthesia and chemotherapy), and athletes use it to track training progress. It is also used to calculate resting metabolic rate more accurately than total body weight.
Is the body fat percentage from this calculator accurate?
It is an estimate based on equations, not a direct measurement. For precise body fat, use DEXA, hydrostatic weighing, or a multi-site skinfold test. This calculator is best for tracking changes over time.
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