Fat-free mass = body weight × (1 − body-fat percentage ÷ 100).
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FFMI Calculator
Determine your Fat Free Mass Index
Enter height, weight, and body-fat percentage to calculate fat-free mass, standard FFMI, and normalized FFMI in metric or US units.
YOUR FFMI
21.2
Excellent
Fat-free mass67.2 kg
Body fat11.8 kg · 15.0%
FFMI21.19
Normalized FFMI21.32
FFMI is an estimate, not a diagnosis or proof of performance-enhancing drug use. Accuracy depends on the body-fat value entered.
NORMALIZED FFMI21.3 · Excellent
Height-adjusted to 1.80 m1417192124262830+
What is FFMI?
FFMI means Fat-Free Mass Index. It compares fat-free body mass with height, helping distinguish how much of total weight comes from lean tissue rather than fat. This makes a fat free mass index more informative than BMI for many strength athletes and regular gym users.
An FFMI calculator still depends on an estimate of body-fat percentage. If that input changes, fat-free mass and FFMI change too. Use the same measurement method when tracking progress over time.
FFMI Formula
The Kouri correction normalizes FFMI to a reference height of 1.80 meters.
FFMI Interpretation
These overlapping fitness-oriented reference descriptions are not clinical classifications. Body-fat range affects how the same FFMI may look, and population-specific research can produce different distributions.
Men’s FFMI reference
FFMIBody fatContext
17–1810–18%Lower muscularity
18–2020–27%Typical range
19–2125–40%Higher fat mass
20–2110–18%Athletic / intermediate
22–236–12%Advanced muscularity
24–258–20%Very high muscularity
Women’s FFMI reference
FFMIBody fatContext
14–1520–25%Lower muscularity
14–1722–35%Typical range
15–1830–45%Higher fat mass
16–1718–25%Athletic / intermediate
18–2015–22%Advanced muscularity
19–2115–30%Very high muscularity
About the frequently quoted “FFMI 25 limit”: a 1995 study of 157 male athletes found normalized FFMI values up to 25 in its non-user sample and described the findings as preliminary. A study of 266 female collegiate athletes reported values ranging from 13.3 to 25.5. A score cannot prove or disprove drug use.
How to Use This FFMI Calculator
- Choose metric or US units.
- Enter your current height and body weight.
- Enter your best available body-fat percentage estimate.
- Read fat-free mass, fat mass, FFMI, and normalized FFMI.
- Repeat with the same body-fat measurement method to track trends consistently.
Research Sources
FFMI Calculator FAQ
What is a good FFMI score?
FFMI varies by sex, age, population, sport, and body-fat measurement method. In common fitness references, values around 21–23 for men are often described as excellent, but no single range applies to everyone.
What is the natural FFMI limit?
There is no definitive individual natural limit. A preliminary 1995 study found normalized FFMI values up to 25 among its male non-user sample. FFMI alone cannot establish whether someone uses performance-enhancing substances.
How is normalized FFMI different from FFMI?
Normalized FFMI adjusts for height using FFMI + 6.3 × (1.80 − height in meters), allowing comparison at a reference height of 1.80 meters.
Does FFMI require body fat percentage?
Yes. This calculator uses body-fat percentage to estimate fat-free mass. If you do not know yours, you can use our AI body fat calculator for a directional photo estimate.
Related Body Composition Tools
⚠ Disclaimer: This FFMI calculator provides an educational estimate only. It is not a medical device and is not intended to diagnose, treat, or prevent any condition. “Natural limit” interpretations are statistical references from published research, not definitive judgments about an individual. Consult a qualified professional for health decisions.