Lean Body Mass Calculator
Calculate your Lean Body Mass (LBM) using the Boer, James, and Hume formulas. Estimate your muscle mass and body fat percentage based on height, weight, and gender.
Optional. Increases accuracy.
What is Lean Body Mass?
Lean Body Mass (LBM) is the weight of your body minus all fat mass. It includes your bones, organs, muscles, skin, and body water. It is sometimes referred to as fat-free mass.
Knowing your LBM is crucial for:
- Medication Dosing: Doctors often use LBM to prescribe drugs (like anesthetics) that are not absorbed by fat.
- Fitness Goals: Tracking LBM helps ensure that weight loss is coming from fat, not muscle.
- Metabolic Rate: LBM is the primary driver of your Basal Metabolic Rate (BMR).
Formulas Used
This calculator uses three standard formulas derived from anthropometric data. If you provide your body fat percentage, we calculate LBM directly from that for maximum accuracy.
- Boer Formula (1984): Often considered the most accurate for non-obese individuals.
- James Formula (1976): A classic formula, though it can underestimate LBM in individuals with high BMI.
- Hume Formula (1966): Another widely used variation similar to Boer.
Why Lean Mass Matters for Weight Loss
When dieting, the scale can be misleading. You might lose weight but actually lose muscle mass, which lowers your metabolism. By tracking your LBM, you can adjust your protein intake (try our Protein Calculator) and resistance training to preserve lean tissue while burning fat.
? Frequently Asked Questions
No. Lean Body Mass includes everything in your body except fat (bones, water, organs, etc.). Muscle mass is a component of Lean Body Mass.
The Boer formula is generally considered the most robust for the average population. If you know your body fat percentage from a DEXA scan or calipers, using that input is far more accurate than any formula.
There is no single 'good' number as it depends heavily on height. Instead, focus on your Body Fat Percentage. For men, 10-20% body fat is healthy; for women, 18-28% is healthy.
Yes. Water makes up a significant portion of your lean tissue (muscles are ~75% water). Dehydration can temporarily lower your calculated LBM if measuring via bioimpedance scales, though these formulas rely on height/weight and won't fluctuate with hydration.