Body measurements · Composition

Lean Body Mass Calculator

Calculate the weight of all your non-fat tissue.

Your details

Sex
Height
Weight
Average lean body mass
53.7kg
By formula
Boer (1984)
54.7 kg
Hume (1966)
51.1 kg
James (1976)
55.3 kg
Implied body fat
23.3%

What is Lean Body Mass?

LBM is the weight of everything except fat — muscle, bone, water, organs, connective tissue. Tracking LBM rather than total weight is the smartest way to know whether a diet preserves the tissue you care about.

The three classic formulas

Boer, Hume and James — averaged for a useful confidence interval.

When LBM is most useful

Dieting (preserve muscle), nutrition planning (protein at ~1.6–2.2 g/kg LBM), drug dosing, resistance-training progress tracking.

Limitations & caveats

  • ±2 kg error for an individual.
  • Not for pregnancy.
  • Less accurate for extreme body-fat %.
  • Use one formula consistently when tracking.
  • DEXA is the clinical reference.
FAQ

Frequently asked questions

Related tools

Keep exploring

Read more

Read up on the science

Understanding BMI in 2026 (understanding bmi) — understanding bmi 2026 illustration
Body Measurements
Feb 12, 2026 6 min read

Understanding BMI in 2026: Beyond the Single Number

BMI is a starting point, not a verdict. Here is how to interpret it with body fat %, waist-to-height and lifestyle context.

By Elements84 Medical Editorial Team
Read
Waist-to-Height (waist to height ratio) — ht the better vital sign illustration
Body Measurements
Feb 10, 2026 5 min read

Waist-to-Height: The Vital Sign That Outperforms BMI

A tape measure and one ratio reveal more about your metabolic risk than the bathroom scale ever could.

By Elements84 Medical Editorial Team
Read
Lean Body Mass (lean body mass) —  mass and why it matters illustration
Body Measurements
Feb 4, 2026 6 min read

Lean Body Mass: The Metric Behind Every Calorie Calculation

Forget your weight. The number that quietly drives your BMR, your protein needs and your training results is the lean mass underneath.

By Elements84 Medical Editorial Team
Read
Kidney anatomy and nephron
Kidney Function & Electrolytes
Jul 20, 2026 9 min read

Creatinine and eGFR: What These Kidney Function Results Mean Together

Understand what creatinine and estimated GFR (eGFR) measure, why eGFR is a calculated estimate rather than a direct measurement, and why one result cannot diagnose chronic kidney disease on its own.

By Elements84 Editorial Team
Read
Medical Evidence

How we ground the Lean Body Mass

Grade B · Observational studiesLast reviewed Nov 1, 2025
Named clinical guidelines
  • Boer P — LBM estimation
  • Hume R — LBM formula
  • James WPT — LBM formula

The Evidence Foundation

Health information should show both what is known and where certainty ends.

Elements84 brings reviewed health evidence, practical decision tools and plain-English explanations together without presenting educational guidance as diagnosis or treatment.

  1. Named sources
  2. Human evidence separated from theory
  3. Limitations shown beside conclusions
  4. Educational, not diagnostic

Reviewed health evidence, practical decision tools and plain-English health education.

Educational information only. Elements84 provides educational information and decision-support tools. It is not a substitute for professional medical advice, diagnosis or treatment.

© 2026 Elements84.