Medical & Fitness Disclaimer
Last updated: 2026-07-07
FFMI Check exists to make peer-reviewed fitness math easier to run. It does not exist to replace a doctor, dietitian, coach, or physiotherapist. Please read the whole page before making training or nutrition decisions based on anything you calculate here.
Educational use only
All calculators, articles, comparison tables, and reference values on this site are provided for educational and informational purposes only. They are not medical, nutritional, or professional fitness advice. They are not a substitute for consultation with a qualified healthcare provider.
Do not use FFMI Check to:
- Diagnose or treat any medical condition
- Design a rehabilitation program after injury
- Manage a chronic condition (diabetes, cardiovascular disease, thyroid disorder, etc.)
- Plan nutrition during pregnancy, lactation, or eating disorder recovery
- Make training decisions for children or adolescents without professional oversight
Accuracy has limits
Every formula on FFMI Check comes with documented accuracy bounds from the source research. In plain terms:
- FFMI depends on an accurate body fat estimate. A 3-point error in body fat moves FFMI by ~1.5 units.
- TDEE using Mifflin-St Jeor is accurate within ±10% for ~82% of healthy adults. It can be significantly off for very muscular, obese, older, or thyroid-affected people.
- US Navy body fat method has ±3–4% accuracy vs DEXA in healthy adults. Higher error at the extremes.
- 1RM estimation with Epley and Brzycki formulas is most accurate at 1–10 reps and degrades above that.
Individual results vary significantly. Treat calculator output as a starting hypothesis, not a diagnosis.
Consult a professional
Consult a qualified professional (physician, registered dietitian, certified strength and conditioning specialist) before:
- Starting an aggressive calorie deficit or bulk
- Adding significant new training volume, especially with prior injury
- Interpreting body composition changes in the context of your health history
- Making decisions during pregnancy, adolescence, or older age
No liability
FFMI Check, its authors, and its operators assume no responsibility for any injury, illness, or adverse outcome resulting from your use of the site or reliance on any calculator or article. You use the information at your own risk.
Affiliate disclosure (FTC / Amazon Associates)
FFMI Check is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. We are also affiliated with other retail and affiliate networks (Admitad, Impact.com, and similar programs).
When you click a product link and complete a purchase, we may earn a small commission from the retailer at no extra cost to you. These commissions help keep FFMI Check free, ad-light, and independently maintained.
Editorial independence. Affiliate relationships never determine what we recommend. Every product we mention has to fit our editorial standard: it must solve a real problem for our audience, it must be objectively good in its category, and its claims must survive the same peer-review scrutiny we apply to formulas. We are not paid to review specific products, and we do not accept free products in exchange for coverage.
How to spot an affiliate link. Product links on FFMI Check may pass through Amazon's tracking parameter (tag=ffmicheck-20) or another affiliate network's tracker. This is standard practice on the modern web. You can always check the destination URL by hovering over any link, and you can always search the product directly without using our link.
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