Lean Body Mass Calculator
Lean body mass is everything except stored fat mass (bones, muscle, organs, water, etc.—including essential fat in organs). This tool applies several published estimating equations side by side. Use metric inputs internally; weights shown in your chosen unit.
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Peters et al. is intended for children roughly 13–14 years and younger.
| Formula | Lean body mass | Est. body fat % |
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Adult equations: Boer (1984), James (1976), Hume (1966). Child equation: Peters et al. (2011). Body fat % ≈ (weight − LBM) / weight. LBM and fat-free mass are related but not identical.