Lean Body Mass Formula
Reference for lean body mass using the Boer, James, and Hume equations.
Used in fitness planning, medication dosing, and body composition analysis.
Need to calculate, not just reference? Use the interactive version.
Open Lean Body Mass Calculator →
The Formula
Boer Formula:
Men: LBM = 0.407W + 0.267H - 19.2
Women: LBM = 0.252W + 0.473H - 48.3
Men: LBM = 0.407W + 0.267H - 19.2
Women: LBM = 0.252W + 0.473H - 48.3
Lean body mass is your total weight minus all fat tissue. It includes muscle, bone, organs, and water. Higher LBM generally indicates better physical fitness.
Variables
| Symbol | Meaning |
|---|---|
| LBM | Lean body mass (kg) |
| W | Body weight (kg). To convert from lbs: divide by 2.205 |
| H | Height (cm). To convert from inches: multiply by 2.54 |
Example 1
A man weighing 85 kg (187 lbs) and 180 cm (5'11") tall
LBM = 0.407 × 85 + 0.267 × 180 - 19.2
LBM = 34.6 + 48.1 - 19.2
LBM ≈ 63.5 kg (estimated body fat ≈ 25.3%)
Example 2
A woman weighing 65 kg (143 lbs) and 165 cm (5'5") tall
LBM = 0.252 × 65 + 0.473 × 165 - 48.3
LBM = 16.4 + 78.0 - 48.3
LBM ≈ 46.1 kg (estimated body fat ≈ 29.1%)
When to Use It
Use the lean body mass formula when:
- Estimating body composition without specialized equipment
- Calculating medication doses based on lean mass
- Setting protein intake and caloric goals for muscle building
- Tracking changes in body composition during training
Key Notes
- For obese patients, use Ideal Body Weight (IBW), not actual weight — the formula overestimates LBM in obesity because adipose tissue does not contribute proportionally to lean mass; many drug dosing protocols specify IBW or adjusted body weight for this reason
- The Boer, James, and Hume equations are all population-average models — they are least accurate at extremes of body size (very tall/short, very lean/obese); DEXA scan or bioelectrical impedance analysis (BIA) give direct body composition measurements
- LBM declines with age (sarcopenia): after age 30, adults lose about 3–8% of muscle mass per decade without resistance training — two people of identical weight and height at different ages can have substantially different LBM values
- Fat-free mass (FFM) and LBM are often used interchangeably but differ slightly: FFM excludes all fat, while LBM includes essential fat (~3% in men, ~12% in women) needed for organ and hormonal function