FFMI Calculator
Calculate your fat-free mass index (FFMI) and normalized FFMI from your height, weight and body fat percentage, and see how it compares with typical and natural-limit ranges. Example: a man 70 in tall at 180 lb and 15% body fat has an FFMI of 22.0 (normalized 22.1).
Show steps
How to use the FFMI Calculator
- Enter the values in the fields.
- Press Calculate to see the result with the steps shown.
Formula and method
FFMI = fat-free mass (kg) / height (m)^2. Normalized FFMI = FFMI + 6.1 x (1.8 – height in m). Fat-free mass = weight x (1 – body fat %).
FFMI categories for men and women
| Category | Men | Women |
|---|---|---|
| Below average | Below 18 | Below 14 |
| Average | 18 to 20 | 14 to 17 |
| Above average | 20 to 22 | 17 to 19 |
| Excellent | 22 to 23 | 19 to 21 |
| Superior | 23 to 26 | 21 and above |
| Suspicious (men) | Above 26 |
Why normalize for height
Taller people carry more lean mass for the same FFMI, so normalizing to 1.8 m makes comparisons fairer across heights.
FFMI versus BMI
BMI counts fat and muscle together. FFMI isolates lean mass, so it suits lifters better, but it needs a body fat estimate.
The natural limit idea
Kouri et al. (1995) found drug-free athletes averaged 22 to 23, with few above 25. Genetics and measurement error mean individuals can fall outside that range.
Frequently asked questions
What is FFMI?
Fat-free mass index: lean mass divided by height squared.
What is a good FFMI?
18 to 20 is average for men; above 22 is notably muscular.
What is the natural FFMI limit?
About 25 for men in the classic study, with caveats.
How do I find my body fat?
Use calipers, a tape-based method, DEXA or an impedance scale.
Is FFMI useful for women?
Yes, with lower ranges.
Why normalize?
To adjust for height differences.
Sources
- Kouri et al., Clin J Sport Med 1995: Fat-free mass index in users and nonusers of anabolic-androgenic steroids
- Schutz, Kyle and Pichard, Am J Clin Nutr 2002: Fat-free mass index and fat mass index percentiles
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