FFMI (fat free mass index) is a formula to quantify muscle development based on your height, weight, and body fat.

With the FFMI calculator, you’ll find your fitness category. See how you compare to your friends and get tips to improve your score.

What Is FFMI?

FFMI is similar to BMI (body mass index). Both categorize people based on height and weight.

But FFMI is generally more accurate for active people because it accounts for body composition. That means it’s a better tool for finding your ideal weight.

FFMI Scale for Men

For men, the FFMI scale generally ranges from 15 to 25. While it’s possible to exceed 25, it’s considered unlikely without the use of steroids.

FFMI Natural Physiques

One study compared 83 steroid users and 74 natural bodybuilders. They concluded that the standardized FFMI for natural athletes extended up to a well-defined limit of 25.0¹.

In addition, the average FFMI for Mr. America winners before 1960 is 25.4¹. This is assumed to be the pre-steroid era of bodybuilding (although that’s debatable).

Despite this data, it is possible to exceed 25 naturally. But it requires good genetics and years of hard work.

FFMI Scale For Women

For women, building muscle is more challenging so the scale ranges from 12 to 22. With anything over 22 considered unlikely without steroids.

Lean Mass & Height

Weight distribution is different for taller and shorter people. For that reason, FFMI is normalized to average height. Or about 5’11” for men and 5’4″ for women. You’ll see both numbers in the results section of the FFMI calculator.

Of course, the taller you are the more lean mass you can fit on your frame. So taller people weigh more at the same FFMI as shorter people.

The graphs below show the FFMI ranges for different heights.

You can use these charts to see how much lean mass you would need to reach the different FFMI categories.

Find your height on the vertical axis and travel across the graph until you intersect the desired category. Then travel down to find your target lean mass on the horizontal axis.

For example, a 5’9″ male would need at least 154 lbs of lean mass to be “extremely muscular”. And a 5’3″ female would need about 101 lbs of lean mass to be “very well built”.

What Is A Good FFMI?

When trying to define a good FFMI, it’s useful to look at a large population. One study sampled over 5,000 men and women and compiled their FFMI data².

I’ve plotted that data here in what’s called a normal distribution or ‘bell curve’. So you can see where the majority of people fall on the FFMI scale.

Based on this data, guys should shoot for an FFMI of at least 19.5 to be above average. But keep in mind this is compared to a random population, not necessarily lifters.

 To stand out among gym bros, you might need to target an FFMI over 21.5

According to these numbers, girls should aim for an FFMI of at least 15.5 to be above average. Again, that’s compared to a random population.

An FFMI above 17.5 would be more likely to get you noticed.

How to Improve FFMI

It’s important to consider body fat along with FFMI when determining how to improve your physique. Because you could have a high FFMI and not be in good shape.

For example, top-level sumo wrestlers are extremely muscular and have very high body fat levels. That’s useful for pushing opponents around, but it’s not the look most of us want.

Therefore, it’s a good idea to focus on reducing body fat if you’re in the overweight or obese categories.

7 Simple Steps To Get Shredded

The “Gym Persona” matrix is intended to make it easy to see which way to go. If you’re in the first two columns you should work on moving to the right.

Once you have your body fat under control, start gaining muscle in order to move down.

More On Muscle Gain Nutrition

At the end of the day, a “good” FFMI is only relative to your starting point. If you’re just beginning, don’t be intimidated by comparing yourself to others. Aim for incremental improvements and strive for your personal best.

Conclusion

FFMI is a useful tool for men and women to assess their current level of fitness. Compared to BMI it’s more accurate and representative of the active population.

In addition, FFMI can predict a naturally attainable goal for your frame. Which helps you determine how to adjust your diet and training to get there.

If you had fun with this FFMI calculator please share it with your friends. And check out my other free tools.

References:
1) Kouri, Elena M., et al. “Fat-free mass index in users and nonusers of anabolic-androgenic steroids.” Clinical journal of sport medicine: official journal of the Canadian Academy of Sport Medicine 5.4 (1995): 223-228.
2) Schutz, Y., U. U. G. Kyle, and C. Pichard. “Fat-free mass index and fat mass index percentiles in Caucasians aged 18–98 y.” International journal of obesity 26.7 (2002): 953-960.