Lean mass guide
Boer vs James vs Hume Lean Body Mass Formulas
Compare the Boer, James, and Hume lean body mass formulas and learn when to use a measured body-fat percentage instead.
Last updated: · Reviewed by the Lean Mass Calculator editorial team
Who this page is for
Users comparing lean body mass formulas before choosing a method.
Start with the main lean mass calculator, then use the related tools below when you need body fat, FFMI, protein, or calorie context.
Interactive Calculator
Use this calculator to find your specific numbers before continuing with the guide.
Formula differences
Boer and Hume are linear equations using weight and height. James includes a squared weight-to-height term, which can behave poorly at higher body weights.
Because formulas do not observe actual body fat, they are best treated as fallback estimates.
Recommended order
Use measured body fat percentage first when you have it. Use Boer as the default formula when you do not.
Use James and Hume mainly for comparison, clinical context, or when a specific reference asks for those equations.
Frequently asked questions
Which lean body mass formula is best?
Measured body fat percentage is best. Without it, Boer is a strong default for general adult use.
Why include older formulas?
James and Hume are still cited in calculators and clinical references, so comparison helps users understand different results.
Sources & references
The estimates on this page use published lean body mass equations and clinical reference ranges. See the full reference charts on the lean body mass chart hub.
- Estimated lean body mass as an index for normalization of body fluid volumes — Boer P, American Journal of Physiology (PubMed) (1984)
- Percent Body Fat Norms and Reference Ranges — American Council on Exercise (ACE)
- Body Composition — Reference Information — National Institutes of Health (NCBI Bookshelf)