ScoutMyTool

Lean Body Mass Calculator

LBM estimate using the Boer formula — weight minus fat mass.

Inputs

30250
120220

Result

Lean body mass (Boer)
58.0 kg
  • Implied fat mass17.0 kg
  • Implied body fat %22.6%
  • LBM — Hume formula54.4 kg
  • LBM — James formula59.0 kg
  • Average across formulas57.2 kg

How to use this calculator

  • Pick your sex and units.
  • Enter weight and height.
  • Use the same formula consistently when tracking changes over time.

About this tool

Lean body mass (LBM) is everything that isn't fat — muscle, bone, organs, water. Knowing your LBM is more useful than scale weight for tracking real progress, especially during cuts (you want to lose fat without losing LBM) or bulks (you want LBM to grow). Three formulas commonly used: Boer (most popular), Hume, and James. They give slightly different estimates because they were calibrated on different populations. For accurate LBM tracking, DEXA scans are the gold standard; these formulas are good ballparks for athletes and routine check-ins.

Frequently asked

Boer is the most common in modern fitness writing. Pick one and stick with it — what matters is the trend over time, not the absolute number from any one formula.

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