How to use
- 1Pick sex and units (kg/cm or lb/in).
- 2Enter weight, height and body fat percentage — use the body fat calculator if you don’t know it.
- 3Read your FFMI, normalized FFMI and lean mass.
- 4Check the interpretation table for your level.
How FFMI is calculated
First the lean mass: weight × (1 − body fat ÷ 100). FFMI = lean mass (kg) ÷ height² (m). Kouri and colleagues (1995) used a normalized FFMI to adjust for height: FFMI + 6.1 × (1.8 − height in m). Example: 82 kg (181 lb), 1.80 m (5′11″) and 15 % body fat → 69.7 kg lean mass and an FFMI of 21.5.
Is 25 really the natural limit?
Kouri’s team studied 157 male athletes and found that those who had never used anabolic steroids topped out at a normalized FFMI of about 25 — hence the “natural limit”. It is not a hard rule: genetics, years of training and measurement error matter (a few points of body fat error can move FFMI by a full point). The bands in the table are approximate guides based on that study and common coaching practice, with lower thresholds for women.
Why FFMI instead of BMI?
BMI cannot tell muscle from fat, so a muscular rugby player or wrestler can look “overweight”. FFMI looks only at lean mass, making it a better gauge of muscular development in athletes. Results are for information only and are not medical advice.
Frequently asked questions
What is a good FFMI?
For men, 18–20 is average, 20–22 trained and 22–23.5 very muscular. Values above 25 are rarely reached naturally.
What is normalized FFMI?
Taller people score a lower FFMI at the same muscularity, so the value is adjusted to a height of 1.80 m. Use it to compare people of different heights.
What is a typical FFMI for women?
Average women usually sit around 15–17; 19+ indicates a well-trained athlete, and above 22 is very rare.
Need a website for your club?
Fast, SEO-friendly websites and Google Ads management for sports clubs, academies and gyms — talk to Webin Agency.