Lean Body Mass Calculator
Estimate lean body mass from weight and height with Boer and James formulas averaged — the number training actually moves. Track muscle, not just scale weight — free, local, informational only.
How to Use the Lean Body Mass Calculator
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Frequently Asked Questions
LBM vs scale weight?
Scale weight mixes fat, muscle, water, and food; LBM isolates fat-free mass. The tool averages Boer and James estimates and derives a body-fat % from the gap: defaults (male, 80 kg, 180 cm) give Boer 61.4, James 62.7, average ≈62.1 kg with ~22% estimated fat.
How to measure body fat?
DEXA gold standard; calipers and smart scales estimate within a few points. Consistent method matters more than absolute accuracy for trends.
Protein from LBM?
1.6–2.2g per kg of lean mass for muscle goals — LBM-based targets beat bodyweight rules for lean and heavy alike.
Is body data uploaded?
No — math runs locally in your browser. Nothing leaves your device.
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Last updated October 2026