To calculate your FFMI, subtract your body fat percentage from 100, divide by 100, multiply by your weight in kilograms, and then divide by your height (in meters) squared.
Formula:
Contents
FFMI = (W × (1 − BF% ÷ 100)) ÷ H²
Table of Variables
| Variable | Meaning |
|---|---|
| FFMI | Fat-Free Mass Index |
| W | Weight (in kg) |
| BF% | Body Fat Percentage |
| H | Height (in meters) |
What is an FFMI Calculator: Easily Calculate Your Fat-Free Mass Index In 2025
You’ve got the muscle. You’ve got the stats. Now you want to know where you really stand. The FFMI Calculator helps you figure out your Fat-Free Mass Index — a number that tells you how muscular you are, without counting fat weight. Think of it as BMI’s smarter, gym-trained cousin.
Unlike weight or BMI alone, FFMI gives a clearer picture of your lean muscle mass. It’s especially popular among athletes and lifters who want to know if their physique lines up with natural limits. Tools like the FFMI Calculator Menno Henselmans, normalized FFMI calculators, and FFMI percentile charts all use this same formula — and now you can, too.
Looking to compare your results? Many lifters use this to explore natural muscle potential, track changes over time, or answer the ever-popular question: “What’s a good FFMI?” Whether you're just curious or chasing elite numbers, this calculator brings clarity to your gains.
