Track your body composition and estimate your fat-free weight using industry-standard scientific formulas.
Lean Body Mass (LBM)—often referred to as fat-free mass—is the amount of weight you carry on your body that is not fat. If you were to strip away all fat tissue from your body, what remains is your lean body mass. This includes your muscles, bones, organs, skin, connective tissues, and body water.
Knowing your LBM is essential for athletes, bodybuilders, and fitness enthusiasts because it gives a much more accurate picture of body composition than total weight or Body Mass Index (BMI). By tracking LBM over time, you can ensure that you are building or maintaining muscle and only losing fat.
The most accurate way to find your LBM is through advanced body composition scans like DEXA (Dual-Energy X-Ray Absorptiometry) or hydrostatic weighing. However, you can estimate it with high accuracy using scientific equations based on your height, weight, and gender:
| Formula Name | Male Equation | Female Equation |
|---|---|---|
| Boer Formula | 0.407 × W + 0.267 × H - 19.2 | 0.252 × W + 0.473 × H - 48.3 |
| James Formula | 1.1 × W - 128 × (W / H)² | 1.07 × W - 148 × (W / H)² |
| Hume Formula | 0.3281 × W + 0.33929 × H - 29.53 | 0.29569 × W + 0.41813 × H - 43.29 |
Where W represents weight in kilograms (kg) and H represents height in centimeters (cm).
It is common to use the terms "lean body mass" and "skeletal muscle mass" interchangeably, but they are not the same:
Since skeletal muscle typically makes up about 40-50% of your total LBM, a change in your LBM is usually a direct indicator of muscle gain or loss.
Building and preserving lean tissue requires a structured training plan and optimal daily nutrition. Here are the core pillars to maximize your lean body mass:
Train with weights 3-5 times per week. Focus on increasing the weight, reps, or sets over time to trigger muscle hypertrophy.
Eat in a small caloric surplus (10-15% above maintenance) for clean muscle growth, or a moderate deficit to drop body fat while preserving lean tissue.
Aim for 1.6 to 2.2 grams of protein per kilogram of body weight daily to repair muscle fibers and support lean tissue synthesis.
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A healthy lean body mass percentage is generally 75-85% for men (15-25% body fat) and 69-79% for women (21-31% body fat). Athletes will often have higher LBM percentages.
Yes, LBM includes all non-fat weight, meaning hydration levels significantly impact your LBM. Water held inside muscles (volumization) counts as lean tissue.
A natural beginner can build 1-2 lbs of lean muscle per month under optimal conditions. For experienced lifters, muscle gains slow down to 0.5 lbs or less per month.
Yes. Commonly known as "body recomposition," this is highly achievable for beginners, individuals returning from a training break, or those with higher body fat percentages who eat high protein.