FFMI Calculator
Fat-free mass index and the height-normalised FFMI from weight and body fat.
About this tool
Choose units and sex, then enter height, weight and body fat percentage. The calculator shows your FFMI, the normalised FFMI adjusted to a height of 1.80 m, your fat-free mass and fat mass, with a plain-English band for the result.
How FFMI is calculated
Fat-free mass index is fat-free mass in kilograms divided by height in metres squared, the same shape as BMI but counting only lean tissue. That stops a muscular person being labelled overweight. Fat-free mass is weight ร (1 โ body fat %). Someone 180 cm tall weighing 80 kg at 15% body fat has 68 kg of fat-free mass and an FFMI of 68 รท 1.8ยฒ = 21.0. Because taller people tend to have slightly lower FFMI, the normalised version adds 6.1 ร (1.8 โ height in metres). In a 1995 study of strength athletes, Kouri and colleagues found drug-free men rarely exceeded a normalised FFMI of about 25, which is why that number is often called the natural limit. Typical untrained men score 18โ20 and women 14โ17. Honest limits: FFMI is only as good as your body fat estimate, which can be several points out, and the bands are rough guides. Not medical advice. The lean body mass calculator estimates fat-free mass from height and weight, the body fat calculator estimates body fat and the BMI calculator gives the classic index. Is BMI accurate? explains why BMI misreads muscular people.
Frequently asked questions
What is a good FFMI?
For men, 20โ22 is above average and 22โ25 is very muscular. For women, 17โ19 is above average.
What is the natural FFMI limit?
Research on drug-free male lifters found few exceeded a normalised FFMI of about 25. It is a rough guide, not a hard limit.
Why is FFMI better than BMI for lifters?
BMI counts all weight, so muscle looks like excess fat. FFMI removes fat mass first.
Is my data saved?
No. The calculation runs in your browser and nothing is stored or sent.