Anthropometric LBM Formulas

This lean body mass calculator estimates fat-free mass from weight and height using three validated equations. The Boer formula — 0.407·W + 0.267·H − 19.2 for men — is the current standard reference; James and Hume provide robustness checks on the same inputs.

Fat Mass and FFMI

Subtracting LBM from body weight gives fat mass, and the implied body fat percentage follows directly. The fat-free mass index (FFMI) — LBM divided by height squared — normalizes lean mass for height so you can compare physiques fairly.

When to Use Direct Body Fat

If you know your body fat percentage from calipers, DEXA, or bioimpedance, enter it in Advanced Options — the calculator then uses LBM = weight × (1 − fat%) instead of the equations, which is more accurate for individuals far from the population average.