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💪 Lean Body Mass Calculator

Calculate your Lean Body Mass (LBM) — your total weight minus body fat — using three validated scientific formulas: Boer (1984), James (1976), and Hume (1966). Also see your fat mass, body fat percentage, and daily protein target.

LBM Formulas

Boer (1984)
Male: (0.407 × kg) + (0.267 × cm) − 19.2
Female: (0.252 × kg) + (0.473 × cm) − 48.3
James (1976)
Male: (1.1 × kg) − 128 × (kg/cm)²
Female: (1.07 × kg) − 148 × (kg/cm)²
Hume (1966)
Male: (0.3281 × kg) + (0.3393 × cm) − 29.5336
Female: (0.2969 × kg) + (0.4135 × cm) − 43.2933

How to Use the LBM Calculator

  1. 1
    Select Gender
    Choose male or female — each formula uses different coefficients for biological sex differences.
  2. 2
    Enter Weight & Height
    Enter your weight in kg or lbs, and height in cm or feet/inches. Metric is recommended for accuracy.
  3. 3
    View Formula Results
    See LBM from all three formulas side by side, plus the average result used for fat mass calculation.
  4. 4
    Check Protein Targets
    Get personalised daily protein recommendations based on your lean body mass.

Example Calculation

Male, 80 kg, 178 cm:

Boer: (0.407×80) + (0.267×178) − 19.2 = 63.4 kg
James: (1.1×80) − 128×(80/178)² = 65.1 kg
Hume: (0.3281×80) + (0.3393×178) − 29.5336 = 63.8 kg
Average LBM = 64.1 kg
Fat Mass = 80 − 64.1 = 15.9 kg  |  Body Fat = 19.9%

Frequently Asked Questions

Lean body mass (LBM) is everything in your body except fat — including muscles, bones, organs, blood, and water. It represents the metabolically active tissue in your body and is a key indicator of fitness and health beyond simple body weight.

LBM includes all non-fat tissue: muscles, bones, organs, skin, and water. Lean muscle mass refers specifically to skeletal muscle. LBM is always higher than lean muscle mass alone. For fitness purposes, most people use LBM as a practical proxy.

LBM drives your resting metabolic rate — more lean mass means more calories burned at rest. It is also critical for strength, immune function, and healthy ageing. Athletes track LBM to monitor muscle gains and ensure fat loss rather than muscle loss when cutting.

The most effective approach is progressive resistance training (weightlifting) combined with adequate protein intake (1.6–2.2 g per kg of LBM per day) and a slight caloric surplus or maintenance. Adequate sleep and recovery are equally important for muscle protein synthesis.

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