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 numbers in the Lean Body Mass Calculator above.
- Press the Calculate LBM button to see the result.
- To try other numbers, change any value and press the button again.
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. James uses 1.1·W − 128·(W/H)² for men and 1.07·W − 148·(W/H)² for women. Hume's 1966 paper gives 0.32810·W + 0.33929·H − 29.5336 for men and 0.29569·W + 0.41813·H − 43.2933 for women, from 29 men and 27 women. The paper says its men's formula applies over age 16 and its women's formula probably only over age 30. None of the three measures your body. Each one predicts lean mass from height, weight and sex, so two people with the same numbers get the same result whatever their build.
Worked example
A 75 kg male at 178 cm by Boer: LBM = 0.407×75 + 0.267×178 − 19.2 = 30.53 + 47.53 − 19.2 = 58.9 kg. This implies body fat mass of 16.1 kg (21.5% 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?
This page does not rank them. Each formula has its own coefficients, so the three results differ for the same height and weight. All three are predictions from height, weight and sex, and none of them measures your body.
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.