Calculate your lean body mass (LBM) using Boer, Hume, and James formulas. Get estimated fat mass and body fat percentage instantly. Free, science-based calculator.
CalcVita. (2026). Lean Body Mass Calculator — 3 Scientific Formulas. CalcVita. Retrieved June 4, 2026, from https://calcvita.com/en/calculators/lean-body-mass
Suggested article
Lean body mass is the weight of everything in your body that is not fat — muscles, bones, organs, and water. Learn how to calculate it using Boer, Hume, and James formulas, and why it matters more than total body weight for health and performance.
Read the full article →This calculator uses three validated formulas — Boer (1984), Hume (1966), and James (1976) — to estimate lean body mass from weight, height, and sex. Lean body mass (LBM) is the portion of your body weight that is not fat. It includes muscles, bones, organs, and body water. The average of all three formulas is displayed as the primary result.
The Boer formula was derived from densitometry studies and is widely used in clinical settings. Hume developed his equation using data from hospitalized patients, making it useful across a broad weight range. The James formula, while simple, can underestimate LBM in individuals with higher BMI. All three are used in drug dosing, sports science, and body composition research.
These formulas were derived from population samples and may not accurately reflect individual body composition. They do not account for ethnicity, fitness level, or disease state. For precise measurements, clinical methods such as DEXA scanning or underwater weighing should be used. Consult a healthcare professional for medical decisions.
More calculators
Body fat calculator
Estimate body fat % using US Navy or CUN-BAE methods.
Ideal weight calculator
Calculate ideal weight using 4 scientific formulas + WHO range.
BMI calculator
Compute your BMI with WHO ranges and guidance.
Protein calculator
Your daily protein needs by weight, activity level and goals (ISSN).
