FFMI Calculator (Fat-Free Mass Index, Normalised)

What this tool does

FFMI is the muscle-and-bone equivalent of BMI: fat-free mass divided by height squared, so it tells a muscular person apart from an overweight one in a way BMI cannot. The normalised value, from a 1995 study by Kouri and colleagues of male athletes, adds 6.1 for every metre below 1.80 m so that tall and short people can be compared. In that study drug-free athletes rarely went above about 25, which popularised the figure as a rough natural ceiling, though later work found exceptions and the number is only as good as the body fat estimate you put in. Typical untrained adults sit well below that: roughly 18–20 for men and 15–17 for women.

Formula

FFMI = fat-free mass (kg) ÷ height (m)² · normalised FFMI = FFMI + 6.1 × (1.80 − height in m)

Variables

Worked example

Limitations

• This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
• The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.