Lean Body Mass Calculator
Fat-Free Mass Estimator
Enter your height, weight, and sex to estimate your lean body mass — no tape measurements required.
Parameters
Lean Body Mass (Boer)
| Boer Formula | -- |
| James Formula | -- |
| Hume Formula | -- |
Understanding Lean Body Mass
Lean Body Mass (LBM) is your total body weight minus fat mass — it includes muscle, bone, organs, and water. Unlike tape-measurement methods, these formulas estimate LBM directly from height, weight, and sex.
Muscle & Bone
LBM includes skeletal muscle and bone density, both of which are key drivers of strength and long-term metabolic health.
Medication Dosing
LBM is used clinically to dose certain medications more precisely than total body weight, since fat tissue processes drugs differently.
Tracking Progress
Watching LBM alongside total weight during a diet helps confirm you're losing fat and not muscle.
Formula-Based, Not Measured
These formulas don't require calipers or scans, but that convenience trades off some individual accuracy compared to DEXA.
The Boer Formula
Men
Women
Where w is weight in kg and h is height in cm. The Boer formula (1984) is widely cited as the most broadly accurate of the height/weight-based LBM equations.
Comparing the Three Formulas
| Formula | Year | Notes |
|---|---|---|
| Boer | 1984 | Most widely cited general-purpose formula |
| James | 1976 | Accounts for the weight/height² relationship directly |
| Hume | 1966 | One of the earliest LBM formulas, still used as a reference |
Important Limitations
- Population averages: These formulas were derived from specific study populations and may be less accurate for very muscular or very obese individuals.
- No direct measurement: A DEXA scan or BOD POD provides a clinically measured value rather than a formula-based estimate.
- Doesn't separate muscle from other lean tissue: LBM includes bone, organs, and water — not muscle mass alone.
Key Takeaways
- LBM is everything that isn't fat. Muscle, bone, organs, and body water all count toward this number.
- Boer is the modern reference formula. It's generally considered the most broadly accurate of the height/weight-based methods.
- Useful for tracking trends. Comparing LBM over time is often more informative than a single snapshot.
- Consult a professional. Formula-based LBM is an estimate — a DEXA scan or BOD POD gives a clinically precise measurement if you need one for medical or performance purposes.