UNDERSTAND THE METHOD
How to use this calculator
Enter waist, height, weight, age, and the source category. Each category has two population equations. This comparison averages their outputs. Choose published coefficients or the high-precision convention observed in other calculators. Enter body fat if known; otherwise the separate BMI estimate supplies composition context.
What the result can tell you
The equations were developed from non-Hispanic White and Black participants. Highly trained athletes and people with catabolic illness were not represented. Averaging two population equations is a calculator convention, not an independently validated combined model. The paper prints rounded coefficients; the longer decimal convention is not independently sourced to an original coefficient file.
Common questions
What inputs does the muscle-mass comparison use?
Enter waist, height, weight, age, and the source category. Each category has two population equations. If body fat is unknown, the separate BMI estimate supplies composition context.
Does the result equal my measured muscle mass?
No. The equations come from specific participant groups, and highly trained athletes and people with catabolic illness were not represented. Averaging the equations is a calculator convention.
Sources & limitations
Sources checked September 12, 2026. These notes identify methods and assumptions. They have not received an independent clinical review.
- Heymsfield and colleagues publish the Series 2 waist equations.frontiersin.org
- BMI-derived body-fat estimation for composition context.pubmed.ncbi.nlm.nih.gov