What is FFMI and how is it calculated?

Fat-Free Mass Index (FFMI) is a measure of lean body mass relative to height. It is calculated as Lean Mass (kg) divided by Height (m) squared, where Lean Mass = Weight × (1 − Body Fat %).

What is Normalized FFMI?

Normalized FFMI adjusts FFMI for height using the formula FFMI + 6.1 × (1.8 − Height in meters), making comparisons across body sizes more meaningful.

What is the natural FFMI limit?

Based on the landmark 1995 Kouri et al. study published in the Clinical Journal of Sport Medicine, an FFMI around 25 is considered the natural ceiling for drug-free male athletes. Values above 25 are statistically uncommon without pharmacological assistance.

How accurate is TDEE from the Mifflin-St Jeor equation?

Mifflin-St Jeor is considered one of the most accurate predictive BMR equations for healthy adults. TDEE is BMR multiplied by an activity factor and is a strong starting point that should be adjusted based on real-world weight trends.

About FFMI Check

FFMI Check is a free, evidence-based fitness calculator hub focused on the numbers that actually matter for anyone who lifts weights: Fat-Free Mass Index (FFMI), Total Daily Energy Expenditure (TDEE), macronutrient splits, body fat percentage, and one-rep-max estimation.

Why This Site Exists

Most online fitness calculators are wrong, incomplete, or aggressively monetized. They pick one formula, give you a number, and disappear — no context about accuracy, no verification protocol, no explanation of which of the 5+ available formulas actually fits your body type. The result: lifters make training and nutrition decisions based on numbers that are often off by 10-30%.

FFMI Check exists to fix this. Every calculator on the site is:

Anchored to peer-reviewed research — Kouri et al. (1995) for FFMI ceilings, Mifflin-St Jeor (1990) for TDEE, Morton et al. (2018) for protein requirements, Helms et al. (2014) for contest-prep macros, Epley and Brzycki for 1RM estimation
Compared side-by-side with alternatives so you understand what you are choosing between
Explained in editorial depth — every calculator sits inside a 1,500-2,500 word article covering the formula's origin, accuracy range, common misuse patterns, and calibration protocol
Free forever — no signup, no email capture, no paywall on any tool or article

Our Editorial Standards

Every article on the site follows a consistent standard:

1,500-2,500 words of original editorial content — no thin content, no listicle filler
Named citations to primary sources — actual study names, authors, and years, not vague "studies show" phrasing
Direct-answer format — every H2 followed by a clear, definitive answer for the query it addresses
No AI-generated boilerplate — every article is written or heavily edited by hand
Comparison tables and worked examples with real numbers — not abstract theory
Related reading cross-links to sibling articles for deeper context
Regular updates — modified dates reflect actual content revisions, not automated timestamp bumps

Who Runs This Site

FFMI Check is an independent publication run by Sami Renkyörgancı, based in Konya, Turkey. Sami is a solo founder with a background in software engineering and data analysis, applying that lens to fitness content: peer-reviewed research, statistical rigor, and honest presentation of what the numbers actually mean.

The site does not have an editorial team or paid contributors. Every article, calculator, and design decision comes from one person building in public. This is intentional — a smaller, focused editorial voice produces more consistent content than a rotating cast of freelance writers.

Research Sources We Cite

The peer-reviewed anchor citations you will see repeated across articles:

Kouri et al. (1995) — Fat-free mass index in users and nonusers of anabolic-androgenic steroids (Clinical Journal of Sport Medicine)
Mifflin, St Jeor et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals (American Journal of Clinical Nutrition)
Morton, McGlory, Phillips (2018) — A systematic review and meta-analysis of protein supplementation and resistance training (British Journal of Sports Medicine)
Helms et al. (2014) — Evidence-based recommendations for natural bodybuilding contest preparation (Journal of the International Society of Sports Nutrition)
Aragon and Schoenfeld (2013) — Nutrient timing revisited (Journal of the International Society of Sports Nutrition)
Frankenfield et al. (2005) — Comparison of predictive equations for resting metabolic rate (Journal of the American Dietetic Association)

What We Are Not

Not a medical resource. FFMI Check publishes fitness and physique content. Nothing on this site is medical advice. Consult a physician for health decisions.
Not a coaching service. We do not offer 1-on-1 coaching, programming, or nutrition consultations.
Not a supplement seller. We are not affiliated with any supplement brand and do not sell products directly.
Not politically neutral on training methods. We favor evidence-based, natural-lifting-oriented content. Enhanced physique content is analyzed but not celebrated.

Monetization Disclosure

FFMI Check funds itself through two mechanisms:

1. Display advertising — via Google AdSense on select pages. Ads are placed to avoid disrupting the reading experience. 2. Amazon Associates affiliate links — when we recommend a specific product (body-composition scale, food scale, fitness book), the links are affiliate links. Amazon pays a small commission on qualifying purchases at no additional cost to you.

Full disclosure appears in the affiliate disclosure page, and every affiliate link on the site is marked with rel="sponsored" per FTC guidelines.

Contact

For corrections, feedback, media inquiries, or advertiser questions, see the Contact page.

---

Site launched: 2026. Publisher: Sami Renkyörgancı (Konya, Turkey). Last updated: 2026-09-30.

← Back to FFMI Check