Your fat-free mass index
Evaluates muscle development relative to height.
What Is FFMI?
FFMI (fat-free mass index) shows the level of muscle in your body relative to height; think of it as a muscle-focused version of BMI. BMI looks at total weight, while FFMI considers only lean mass.
This lets muscle development be evaluated independently of height, fairly comparing people of different heights. General reference: 18–22 normal, 22+ athletic for men; the range is lower for women.
Since the value is based on lean mass, its accuracy depends on the body fat percentage you enter; treat the result as an estimate.
How Is FFMI Calculated?
FFMI shows the level of muscle and other lean tissue relative to height. BMI considers total weight, while FFMI considers only lean mass.
The calculation has two steps. First lean mass is found from body fat percentage, then that value is divided by the square of height:
Weight is in kilograms and height in metres.
Calxin also provides a height-adjusted FFMI, which balances the difference between tall and short people for a more consistent comparison:
As a general reference, FFMI is considered 18–22 normal and 22+ athletic for men; lower for women. These are guidance ranges, not strict limits.