🏆 Medical-Grade Accuracy

Lean Body Mass Calculator 2025

Calculate your lean body mass instantly with our medically accurate, free calculator using 4 proven formulas trusted by fitness professionals worldwide. Get comprehensive body composition analysis and insights.

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4 Proven Formulas

Calculate Your Lean Body Mass

Enter your details to get instant, medically accurate lean body mass calculations using 4 proven formulas

years
Age 14 or younger uses Peters formula
cm
Required for all LBM calculations
kg
Current body weight for LBM calculation

Your Lean Body Mass

Boer Formula
(1984)
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Most widely used
James Formula
(1976)
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Conservative estimate
Hume Formula
(1966)
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Clinical standard

LBM Formulas

Adult Formulas

Boer (1984):
Male: 0.407×W + 0.267×H - 19.2
Female: 0.252×W + 0.473×H - 48.3
James (1976):
Male: 1.1×W - 128×(W/H)²
Female: 1.07×W - 148×(W/H)²
Hume (1966):
Male: 0.32810×W + 0.33929×H - 29.5336
Female: 0.29569×W + 0.41813×H - 43.2933

Children Formula

Peters (2011):
eECV = 0.0215×W^0.6469×H^0.7236
LBM = 3.8×eECV
W = Weight (kg), H = Height (cm). Results in kg.

⚠️ Medical Disclaimer

This lean body mass calculator is for informational purposes only. LBM formulas provide estimates and may not account for individual variations in body composition. Results should not replace professional medical evaluation. Always consult healthcare professionals for medical decisions.

Understanding Lean Body Mass (LBM)

Comprehensive guide to lean body mass, body composition, and everything you need to know about muscle mass and fat distribution.

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What is LBM?

Lean Body Mass (LBM) is the weight of everything in your body except fat, including muscles, bones, organs, blood, and water. It typically represents 60-90% of total body weight.

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LBM vs Fat-Free Mass

LBM includes essential fat in organs, while fat-free mass excludes all fat. The difference is about 2-3% in men and 5-12% in women, making LBM slightly higher than fat-free mass.

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Medical Applications

LBM is crucial for medical dosing, especially for water-soluble drugs and anesthetics. Many medications are dosed based on LBM rather than total body weight for better accuracy.

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Formula Differences

Different formulas yield varying results. Boer is most widely used, James provides conservative estimates, Hume is the clinical standard, and Peters is specifically for children 14 and under.

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Fitness Applications

LBM helps track muscle gain/loss during training. Higher LBM indicates more muscle mass, which increases metabolism and improves overall health and athletic performance.

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Body Composition Goals

Focus on maintaining or increasing LBM while managing body fat. A higher LBM percentage indicates better health, metabolic efficiency, and physical function throughout life.

Frequently Asked Questions

Everything you need to know about lean body mass calculations, body composition, and their practical applications answered by health experts.

What is a good lean body mass percentage?

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LBM typically ranges from 60-90% of total body weight. Men generally have 75-90% LBM, while women have 65-85% due to naturally higher essential fat. Athletes often have higher percentages due to increased muscle mass.

Which LBM formula is most accurate?

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The Boer formula is most widely used and generally considered most accurate for adults. For children 14 and under, the Peters formula is specifically designed. Consider averaging multiple formulas for a more comprehensive estimate.

How can I increase my lean body mass?

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Increase LBM through resistance training, adequate protein intake (0.8-1.2g per kg body weight), progressive overload, sufficient rest, and proper nutrition. Building muscle while maintaining low body fat optimizes LBM percentage.

Why is LBM important for medical dosing?

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Many drugs, especially water-soluble ones and anesthetics, are better dosed based on LBM rather than total weight. This provides more accurate dosing, especially in overweight individuals where fat tissue doesn't significantly affect drug metabolism.

Does LBM change with age?

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Yes, LBM typically decreases with age due to muscle loss (sarcopenia), starting around age 30. Regular resistance training, adequate protein, and staying active can help preserve LBM throughout life.

How does LBM relate to metabolism?

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LBM is the primary determinant of metabolic rate. Muscle tissue burns more calories at rest than fat tissue. Higher LBM means higher metabolism, making weight management easier and improving overall health.