Calculate your Fat-Free Mass Index (FFMI) instantly with our free FFMI Calculator.
| Fat Free Mass | 0 lbs |
| Body Fat | 0 % |
| FFMI | 0 |
| Normalized FFMI | 0 |
What is FFMI?
FFMI, or Fat-Free Mass Index, is a measure used to estimate how much lean muscle mass you have in relation to your height. Unlike the traditional BMI (Body Mass Index), which includes both fat and muscle, FFMI focuses solely on fat-free body mass—making it a preferred metric for athletes, fitness enthusiasts, and bodybuilders.
FFMI helps determine whether your physique falls within natural limits or may indicate performance enhancement. It’s a more accurate reflection of muscularity and body composition, especially for those who train regularly.
FFMI Formula
To calculate FFMI, you need your weight, height, and body fat percentage. Here’s how it works:
- Total Body Fat = Weight × (Body Fat [%] ÷ 100)
- Lean Body Mass = Weight × (1 − (Body Fat [%] ÷ 100))
- FFMI = (Lean Mass in kg) ÷ (Height in meters)²
- In imperial units:
FFMI = (Lean Weight / 2.2) / ((Feet × 12 + Inches) × 0.0254)²
- In imperial units:
For more accurate results, especially when comparing individuals of different heights, you can use the Adjusted FFMI:
- Adjusted FFMI = FFMI + (6.3 × (1.8 − Height in meters))
This adjusted value normalizes FFMI to a reference height of 1.8 meters (about 5 ft 11 in), offering a fair comparison across all heights.
FFMI Interpretation
Understanding your FFMI score can help you evaluate your physique based on your level of fitness or muscular development. FFMI interpretations vary for men and women:
FFMI Scale for Men
| FFMI Score | Body Fat % | Classification |
|---|---|---|
| 17–18 | 10–18% | Lean or under-muscled |
| 18–20 | 20–27% | Average build |
| 19–21 | 25–40% | Higher fat percentage |
| 20–21 | 10–18% | Athletic / Regular gym-goer |
| 22–23 | 6–12% | Advanced level fitness enthusiast |
| 24–25 | 8–20% | Bodybuilder / Powerlifter / Weightlifter |
FFMI Scale for Women
| FFMI Score | Body Fat % | Classification |
|---|---|---|
| 14–15 | 20–25% | Lean or under-muscled |
| 14–17 | 22–35% | Average build |
| 15–18 | 30–45% | Higher fat percentage |
| 16–17 | 18–25% | Athletic / Regular gym-goer |
| 18–20 | 15–22% | Advanced level fitness enthusiast |
| 19–21 | 15–30% | Bodybuilder / Powerlifter / Weightlifter |
How to Use the FFMI Calculator
You can easily estimate your FFMI by following these steps:
- Select your measurement system – Choose between Imperial (feet, pounds) or Metric (cm, kg).
- Enter your height – Input your exact height in either feet/inches or centimeters.
- Enter your weight – Provide your current body weight.
- Enter your body fat percentage – You can get this from a smart scale, calipers, or professional scan.
- Click “Calculate” – The calculator will instantly show your FFMI and adjusted FFMI.
Why FFMI Matters
FFMI is a more precise way to assess muscular development, especially for those focused on strength training or bodybuilding. Whether you’re tracking your natural muscle growth or evaluating physique goals, FFMI gives you a clearer picture of your progress than BMI alone.
FAQs for FFMI Calculator
What is a good FFMI score?
A good FFMI score typically ranges from 18 to 22 for men and 14 to 18 for women. Scores above these ranges may indicate advanced muscle development or, in some cases, unnatural enhancement.
What is the difference between FFMI and BMI?
While BMI (Body Mass Index) measures body weight relative to height (including fat and muscle), FFMI (Fat-Free Mass Index) focuses only on lean muscle mass, making it more accurate for athletes and fitness enthusiasts.
Can FFMI detect steroid use?
FFMI can suggest potential unnatural muscle mass levels. An FFMI above 25 for men or above 21 for women may indicate the possibility of performance-enhancing drug use, though it’s not a definitive test.