LEAN BODY MASS
CALCULATOR

Estimate your lean body mass — muscles, organs, bone, and water — using the validated Boer formula.

✅ Boer Formula💪 Muscle vs Fat Mass📋 Medically Reviewed
Your Details
Your Lean Body Mass
--
Lean Body Mass (kg)
💪 Lean Body Mass (Boer)--
📈 Estimated Fat Mass--
📈 Body Fat %--
📈 LBM as % of Body Weight--
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LBM Reference Ranges

ProfileLean Body Mass %Body Fat %
Athletic man80–90% LBM10–20% body fat
Athletic woman75–85% LBM15–25% body fat
Average adult70–80% LBM20–30% body fat
Sedentary adult60–75% LBM25–40% body fat

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What Is Lean Body Mass?

Lean Body Mass (LBM) is the weight of everything in your body except fat: muscles, bones, organs, water, and connective tissue. It is sometimes used interchangeably with Fat-Free Mass (FFM), though technically LBM includes a small amount of essential fat. LBM is a useful metric for setting protein targets and tracking body composition changes over time. In clinical settings, professionals may also reference LBM for purposes such as medication dosing, but that application requires proper testing and supervision by a qualified provider — not a free online estimate.

Why LBM Matters

LBM is the metabolically active portion of your body. Higher LBM correlates with higher BMR (you burn more calories at rest), better insulin sensitivity, stronger bones, and better functional outcomes in aging. Preserving LBM during caloric restriction is a primary goal of evidence-based fat loss protocols — which is why higher protein intake and resistance training are commonly recommended while dieting.

The Boer Formula

The Boer formula estimates LBM from height and weight: for men, LBM = (0.407 × kg) + (0.267 × cm) − 19.2; for women, LBM = (0.252 × kg) + (0.473 × cm) − 48.3. It is one of the most validated LBM estimation formulas for general populations, though DEXA scan remains the gold standard.

SM
Medically Reviewed by Dr. Sarah Mitchell, M.D.
Board-Certified Internal Medicine · 12 Years Clinical Experience
Dr. Mitchell reviews all IndexBody health content for clinical accuracy and alignment with WHO, CDC, and NIH guidelines.

Frequently Asked Questions

What is a healthy lean body mass percentage?
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There is no universal ideal LBM percentage as it varies with sex, age, and athletic status. Generally, athletic men might have 80–90% LBM (10–20% body fat) and athletic women 75–85% LBM (15–25% body fat). Total body weight, lean mass, and body fat percentage must all be considered together.
How do I increase lean body mass?
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Increasing LBM generally requires resistance training combined with adequate protein intake (1.6–2.4g/kg body weight) and, for many people, a slight caloric surplus to support muscle growth. Sleep quality, stress management, and progressive overload in training are also important factors, and individual results vary.
What is the difference between lean body mass and muscle mass?
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Lean body mass includes all non-fat tissue: muscles, bones, organs, water, and connective tissue. Muscle mass refers specifically to skeletal muscle tissue. LBM is always larger than muscle mass and is the value estimated by most body composition tools without DEXA or MRI scanning.
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