FFMI Calculator: Fat-Free Mass Index
Enter height, weight and body fat % to see your fat-free mass index, a BMI-like number that counts only lean mass.
- Nothing you type is stored
- Free
- No signup
Your FFMI
19.3kg/m²
- Normalised FFMI (1.8 m)
- 19.6 kg/m²
- Fat-free mass
- 59 kg
- Fat mass
- 13 kg
- Fat mass index
- 4.2 kg/m²
An estimate for general information, not medical advice.
Reference: drug-free male athletes rarely exceeded a normalised FFMI of about 25 (Kouri et al., 1995).
How to use
- Enter height and weight.
- Enter your body fat % (from a tape, scale or scan).
- Read FFMI, normalised FFMI and fat mass.
Good to know
Fat-free mass = weight × (1 − body fat %). FFMI = fat-free mass ÷ height². Normalised FFMI = FFMI + 6.1 × (1.8 − height in m), which adjusts to a 1.8 m reference so tall and short people can be compared (Kouri et al., 1995).
In the Kouri study of 157 male athletes, drug-free men rarely had a normalised FFMI above about 25. Typical untrained men sit around 17–20 and women around 14–17.
FFMI is only as good as the body fat % you enter; a 3% error in body fat moves FFMI by about 0.6. It is a muscularity measure, not a health score.
Questions
What is a good FFMI?
For untrained men about 17–20, trained men 20–23. For women roughly 14–17 untrained and 17–19 trained. These are rough reference ranges, not targets.
Is an FFMI over 25 possible naturally?
The 1995 Kouri study found it rare among drug-free men, but a few people with unusual genetics do exceed it. It is not proof of anything for an individual.
Why use FFMI instead of BMI?
BMI counts muscle as excess weight. FFMI removes fat so it reflects muscle more fairly.
Where do I get my body fat %?
Use our body fat calculator (tape method), a body fat scale, or a DEXA scan. Use the same method each time.
Is my data stored?
No. Everything is calculated on your device.