FFMI Calculator - Fat-Free Mass Index & Normalised FFMI
FFMI Calculator
How much muscle do you carry for your height?
Muscle, Not Just Weight
Unlike BMI, FFMI leaves out body fat, so a muscular person is not mislabelled as overweight.
Height Normalised
The normalised value adjusts for height so tall and short people can be compared on the same scale.
Both Unit Systems
Switch between kg and cm or lb and inches and your entries convert automatically.
Full Privacy
Everything is calculated in your browser.
What FFMI Tells You
FFMI is lean mass in kilograms divided by height in metres squared, so it is BMI with the fat taken out. The normalised version adds 6.1 × (1.8 − height in metres) to correct for the fact that taller people carry proportionally more lean mass. A 2 kg change in lean mass moves FFMI by only about 0.6 for someone of average height, so it is best used to track trends.
The rating bands come from a 1995 study of male athletes and are only a rough guide. Your result depends heavily on how accurately body fat was measured, which is often off by several percentage points, and no single number proves anything about how someone trained. This is general information, not medical advice.
Key Takeaways
- Standard formula: Uses the published height-normalisation of Kouri and colleagues.
- Honest about limits: Explains that body-fat error dominates the result.
- Information only: Not a diagnosis or medical advice.