What Is Lean Body Mass (LBM)?

Lean Body Mass is everything in your body that isn’t fat. That includes muscle, bones, organs, fluids, and connective tissues. It’s the functional part of your body that supports strength, performance, and energy metabolism.

Why Is LBM Important?

• Metabolism: Muscle tissue is metabolically active—it burns more calories than fat, even at rest. More LBM generally means a higher Resting Metabolic Rate (RMR).
• Strength: Muscle is directly tied to physical strength. Preserving or increasing LBM improves force output and functional performance.
• Stamina and Endurance: A higher LBM supports more efficient energy systems, especially during moderate to high physical effort.
• Longevity: Maintaining LBM helps protect mobility, balance, and independence with age. Low muscle mass is linked to frailty and poorer health outcomes.

How Accurate Is This Calculator?

This tool estimates your LBM based on your current body weight and body fat percentage. If you entered your body fat percentage from a reliable method (like DEXA, bioelectrical impedance, or skinfolds), the calculation is generally quite accurate. If you guessed or used a visual chart, it’s an estimate—but still helpful for tracking progress over time.

Why Should You Track It?

Most weight loss efforts don’t distinguish between fat loss and muscle loss—but they should. Tracking your LBM helps ensure you're losing fat while preserving (or even building) muscle. If you're gaining weight, knowing your LBM helps you confirm whether it's muscle or fat.

How to Use LBM in Meal Planning and Training

• Protein Needs: Most recommendations for protein are based on LBM. A typical target is 1.2–2.2g of protein per kg of LBM per day, depending on goals.
• Goal Tracking: Use LBM alongside weight and body fat changes to assess whether your plan is improving body composition.
• Metabolic Estimates: LBM influences your RMR. Use your LBM to better predict calorie needs and customize your training and nutrition plans.