The FFMI Calculator (Fat-Free Mass Index) (lbs/m²) measures your muscle mass relative to your height. Unlike BMI, which includes body fat, FFMI focuses on your lean body mass. Many athletes, bodybuilders, and fitness enthusiasts use this calculator to track muscle gain while keeping fat levels in check. This calculator falls under the Body Composition Calculator category. It helps you understand whether your muscle mass is within a healthy or achievable range based on your height.
formula of FFMI Calculator (Fat-Free Mass Index)
FFMI = (Fat-Free Mass in lbs) / (Height in meters)²
Step-by-step:
- Calculate Fat-Free Mass (FFM):
FFM = Body Weight × (1 − Body Fat Percentage)
Body Weight must be in pounds (lbs)
Body Fat Percentage must be a decimal (for example, 15% is 0.15)
- Convert height to meters:
Height (m) = Height (inches) × 0.0254 - Plug the values into the FFMI formula:
FFMI = FFM (lbs) / [Height (m)]²
Quick FFMI Reference Table
This table shows average FFMI values to help you compare without always calculating.
| FFMI Value | Category |
|---|---|
| 16–17 | Below Average Muscle Mass |
| 18–19 | Average Muscle Mass |
| 20–21 | Above Average Muscle Mass |
| 22–23 | Excellent Muscle Mass |
| 24–25 | Highly Muscular (Natural Limit) |
| 26+ | Possible Steroid Use (Rare Naturally) |
This general table helps you check where you stand quickly. Always remember that individual factors may vary.
Example of FFMI Calculator (Fat-Free Mass Index)
Let’s see a simple example:
You weigh 180 lbs and have a body fat percentage of 15%. Your height is 70 inches.
- FFM = 180 × (1 − 0.15)
FFM = 180 × 0.85
FFM = 153 lbs - Height in meters = 70 × 0.0254
Height = 1.778 meters - FFMI = 153 / (1.778)²
FFMI = 153 / 3.16
FFMI ≈ 48.42
However, this result uses lbs in the FFM but the classic FFMI formula is originally designed with FFM in kg. To match the classic approach, convert FFM to kg (153 lbs ÷ 2.20462 ≈ 69.4 kg). Then,
FFMI (classic) = 69.4 / (1.778)² ≈ 21.95
This shows a healthy, muscular build.
Most Common FAQs
A good FFMI score is between 18 and 21 for most people. Scores above 23 are rare naturally and may suggest very high muscle mass or possible steroid use.
BMI checks body weight in general, including fat and muscle. FFMI only measures muscle mass compared to your height, giving a clearer view for athletes or fitness enthusiasts.
Yes. FFMI helps you see if you are losing fat but keeping muscle. Many people use FFMI with body fat percentage to check true fitness progress.