Lean mass guide
Lean Mass Calculator for Cutting
Use lean mass to track fat loss, set protein targets, and reduce unnecessary muscle loss during a calorie deficit.
Last updated: · Reviewed by the Lean Mass Calculator editorial team
Who this page is for
People dieting for fat loss while trying to preserve lean mass.
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.
What to watch during a cut
Scale weight alone cannot tell whether a deficit is coming from fat or lean tissue. Pair body weight with lean mass or body-fat tracking.
A small lean-mass fluctuation is normal because glycogen and water change. A sustained downward trend deserves attention.
Protein and calories
The calculator gives a simple protein target from lean body mass. For a range, use the protein calculator and select the fat loss goal.
For calories, estimate TDEE first, then use a moderate deficit and adjust from real trend data.
Frequently asked questions
How often should I recalculate lean mass while cutting?
Every two to four weeks is enough for most people, as long as measurements are taken consistently.
Can lean mass go up during a cut?
Yes, especially for beginners, returning lifters, or people improving training and protein intake.
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)