What Lean Body Mass Includes
Lean body mass (LBM) is your total body weight minus stored fat. It comprises skeletal muscle, bone, organs, skin, connective tissue, and water. For most men, LBM runs about 75–85% of total weight; for women, 65–75%. These ranges shift with age, training history, and body composition.
The Boer Formula
This calculator uses the Boer equations, derived from regression analysis against DEXA measurements:
- Men: LBM (kg) = (0.407 × weight kg) + (0.267 × height cm) − 19.2
- Women: LBM (kg) = (0.252 × weight kg) + (0.473 × height cm) − 48.3
Accuracy is typically ±5–10% for people with average body compositions. For competitive bodybuilders or individuals with obesity, DEXA, hydrostatic weighing, or air displacement plethysmography provides greater precision (±1–2%).
How to Apply Your LBM
- Protein target: Research supports 0.7–1.0 g of protein per pound of LBM to maintain muscle during a calorie deficit.
- Track fat vs. muscle loss: Re-measure LBM every 4–6 weeks. A drop in LBM alongside weight loss means the deficit is too large, or protein intake is too low.
- Resting metabolic rate: LBM is the primary driver of BMR. Each additional kilogram of lean mass adds roughly 13 calories/day at rest.
LBM Reference Ranges
| Fitness Level | Men (LBM%) | Women (LBM%) |
|---|---|---|
| Athletic / Very lean | 88–92% | 80–86% |
| Fit | 80–88% | 72–80% |
| Average | 72–80% | 64–72% |
| Above-average body fat | 60–72% | 55–64% |