Lean Body Mass Calculator
Calculate your lean body mass (LBM) — total weight minus fat mass — using established medical formulas (Boer, James, Hume).
How to use the Lean Body Mass Calculator
- Enter your inputs into the Lean Body Mass Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The LBM formulas
Boer men: 0.407·W + 0.267·H − 19.2 · · · Boer women: 0.252·W + 0.473·H − 48.3
W is total weight in kg, H is height in cm. Boer is the most-commonly cited formula. James and Hume use similar height-and-weight inputs with different coefficients. Results are estimates within ±5%.
Worked example
A 75 kg male at 178 cm by Boer: LBM = 0.407×75 + 0.267×178 − 19.2 = 30.5 + 47.5 − 19.2 = 58.8 kg. This implies body fat mass of 16.2 kg (21.6% BF).
Frequently asked questions
What's LBM used for?
Medication dosing (especially chemotherapy and anesthesia), calorie targets via the Katch–McArdle formula, and setting protein intake targets when training for strength or hypertrophy.
Which formula is most accurate?
Hume is often cited as the most accurate for general adult populations. James was developed in the UK and tends to slightly underestimate. Boer is most widely used in clinical pharmacy.
How does LBM compare to body fat percentage?
Body fat % = (Total weight − LBM) / Total weight × 100. The two metrics are complementary — many practitioners use both for a fuller picture.