FFMI Calculator

Fat-free mass index with natural muscle limit rating

Quick Answer

FFMI Calculator: Fat-free mass index with natural muscle limit rating. FFMI = lean mass (kg) ÷ height(m)², lean mass = weight × (1 − body fat%).

Height (cm)

Weight (kg)

Body fat %

FFMI（fat-free mass index）

20.8

Normalized to 1.8m: 21.1 · lean mass 63.8kg · BMI 24.5

FFMI scale (male reference)

Low

Average

Trained

Advanced

Elite

Suspicious

FFMI 20.8

Steps

1Lean mass = 75kg × (1 − 15%) = 63.8kg
2FFMI = 63.8 ÷ 1.75² = 20.82
3Normalized = FFMI + 6.1 × (1.8 − 1.75) = 21.12

Interpretation

<16Below average muscle

16-18Typical untrained

18-20Regular training

20-22Years of serious training

22-25Natural genetic limit zone

>25Exceeds natural ceiling (Kouri 1995 study)

💡 The landmark Kouri 1995 study found natural bodybuilders peaked at normalized FFMI ≈ 25 — above that suggests pharmacological aid. FFMI is a far better muscle tracker than BMI for lifters: a muscular 100kg at 12% fat can read "obese" on BMI. Female scales run ~2-3 points lower.

Was this tool helpful?

How to Use

Enter body metrics: fill height, weight, age etc. as prompted by the FFMI Calculator.
Read value and grade: results appear instantly with an authority-based classification.
Check reference tables: confirm your range and healthy targets against the tables on this page.
Back-solve your goal: adjust inputs to see what it takes to reach a target.

Key Points

FFMI Calculator is a free online health tool — open and use, no sign-up.
All calculations run locally in your browser; your data never leaves the device.
Key capability: Fat-free mass index with natural muscle limit rating.
Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Fat-free mass index

FFMI = lean mass (kg) ÷ height(m)², lean mass = weight × (1 − body fat%)

Adjusted FFMI = FFMI + 6.3 × (1.8 − height m), normalized to 1.8 m

Male scale: <17 below avg / 17–19 avg / 19–21 above avg / 21–23 excellent / 23–25 near natural limit / >25 beyond

Natural ceiling ≈ 25 (Kouri 1995)

Example: 1.75 m, 80 kg, 15% BF → lean 68 kg, FFMI ≈ 22.2, adjusted ≈ 22.5 ("excellent").

FAQ

How do I use the FFMI Calculator?

Open the page and fill in the input fields — results update automatically. Fat-free mass index with natural muscle limit rating.

Are the results accurate?

Results follow published international standards (WHO, ACE, IOM) and are for reference only.

Can this replace medical advice?

No. Always consult a qualified healthcare professional for health decisions.

Is it free? Do I need to sign up?

Completely free. No registration, login or download required.

Does it work on mobile?

Yes. The responsive design works on all devices.

Related Guides

Source & Updates

Based on WHO, ACE, IOM and other published international standards. Last updated: 2025-07

Authoritative sources:

Last updated: 2026-08-04

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Cite this page: YiJianSuan. FFMI Calculator[EB/OL]. https://www.yijiansuan.com/en/c/health/ffmi

Results provided by this tool are for reference only and do not constitute professional advice.