Lean Body Mass Calculator

The Lean Body Mass (LBM) Calculator estimates your fat-free body weight using three scientifically validated formulas. LBM includes everything in your body except fat: muscles, bones, organs, blood, and water.

What is Lean Body Mass?

Lean Body Mass (LBM), also called Fat-Free Mass (FFM), represents the total weight of your body minus all fat tissue. It's a crucial metric for:

• Medication dosing - Many drugs are dosed based on LBM rather than total weight
• Metabolic assessment - LBM is the primary driver of resting metabolic rate
• Fitness tracking - Monitor muscle gain during training programs
• Nutrition planning - Protein requirements are often based on LBM

Formulas Used

Boer Formula (1984)

Considered the most accurate for general populations.

Men: LBM = (0.407 × weight) + (0.267 × height) - 19.2 Women: LBM = (0.252 × weight) + (0.473 × height) - 48.3

Hume Formula (1966)

Often used in clinical settings for critically ill patients.

Men: LBM = (0.32810 × weight) + (0.33929 × height) - 29.5336 Women: LBM = (0.29569 × weight) + (0.41813 × height) - 43.2933

James Formula

Suited for younger, leaner adults.

Men: LBM = (1.1 × weight) - 128 × (weight/height)² Women: LBM = (1.07 × weight) - 148 × (weight/height)²

Note: All formulas use weight in kg and height in cm

Healthy Lean Body Mass Ranges

Men

Women

Why Use Multiple Formulas?

Each formula was developed for different populations and validated in different studies. By comparing results from all three, you get:

1. A range of estimates rather than a single potentially inaccurate number
2. Better accuracy by averaging or identifying outliers
3. Context for clinical decisions when one formula may be more appropriate

Frequently Asked Questions

Q: Which formula should I use? A: The Boer formula is generally most accurate for healthy adults. Hume is preferred in clinical/hospital settings. James works well for lean, young individuals.

Q: How accurate are these formulas? A: Estimates are typically within ±5% of DEXA scan results. For more precision, consider hydrostatic weighing or DEXA scanning.

Q: What's the difference between LBM and muscle mass? A: LBM includes all non-fat tissue (muscles, bones, organs, water, etc.). Muscle mass is just the muscle portion of LBM.

Q: Can I increase my lean body mass? A: Yes! Resistance training combined with adequate protein intake (1.6-2.2g per kg body weight) promotes muscle growth and increases LBM.

Q: Why does LBM matter for medications? A: Fat tissue doesn't metabolize drugs the same way lean tissue does. Dosing based on LBM ensures more accurate drug distribution and effectiveness.

Disclaimer: This calculator provides estimates only. For precise body composition analysis, consult a healthcare professional or use methods like DEXA scanning or hydrostatic weighing.