FFMI Calculator
Calculate your Fat-Free Mass Index
FFMI Calculator
Calculate your Fat-Free Mass Index
How it works
FFMI (Fat-Free Mass Index) measures how much muscle you carry relative to your height — think of it as a BMI that ignores body fat. It is widely used to gauge muscular development and to discuss the natural muscle-building ceiling.
The calculator works out your fat-free mass from your weight and body-fat percentage, divides it by height squared, and normalizes it to a height of 1.8 m. If you don't know your body fat, the built-in US Navy estimator works it out from a few tape measurements.
As a rough guide: below 18 is below average, 18–20 average, 20–22 above average, 22–25 excellent, and above 25 is elite. Drug-free athletes rarely exceed an FFMI of around 25.
Frequently Asked Questions
What is a good FFMI score?
Below 18 is below average, 18–20 is average, 20–22 is above average, 22–25 is excellent, and above 25 is elite. Natural athletes rarely exceed 25.
Do I need my body-fat percentage?
Yes — FFMI is based on fat-free mass. If you don't know it, use the built-in US Navy estimator, which calculates body fat from neck, waist (and hip) measurements plus height.
Calculations are estimates for educational purposes. Consult a professional before starting any new diet or exercise program.