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Lean Body Mass Calculator
Estimate fat-free mass (LBM) using Boer, Hume, and James formulas. Useful for protein-intake targets and tracking body recomposition.
HEALTHEstimate fat-free mass (muscle, bone, organs, water — everything except fat) using three established formulas: Boer, Hume, and James. Useful for setting protein targets and tracking body recomposition.
Boer: best general accuracy for adults. Hume: developed for clinical use, similar accuracy. James: simpler, less precise for very tall or short people. The three are averaged for a robust point estimate. Multiply LBM by 1.6-2.2 g/kg to get a recomp/lean-bulk protein target.
Disclaimer: Anthropometric estimates are accurate to ±5-10% for typical adults. They under-estimate for very muscular people and over-estimate for sedentary people. For higher accuracy, use DEXA, BodPod, or hydrostatic weighing.
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Frequently Asked Questions
What is the Lean Body Mass Calculator for?
Estimate fat-free mass (muscle, bone, organs, water — everything except fat) using three established formulas: Boer, Hume, and James. Useful for setting protein targets and tracking body recomposition.
How do I use the Lean Body Mass Calculator?
Boer: best general accuracy for adults. Hume: developed for clinical use, similar accuracy. James: simpler, less precise for very tall or short people. The three are averaged for a robust point estimate. Multiply LBM by 1.6-2.2 g/kg to get a recomp/lean-bulk protein target.
How accurate are my lean body mass results?
Anthropometric estimates are accurate to ±5-10% for typical adults. They under-estimate for very muscular people and over-estimate for sedentary people. For higher accuracy, use DEXA, BodPod, or hydrostatic weighing.
Is the Lean Body Mass Calculator free to use?
Yes - every calculator on WhichCalc is completely free with no signup, no usage limits, and no tracking on the calculation itself. Results display instantly in your browser and your inputs are never sent to a server. Bookmark the page if you use this calculator regularly.
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