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FFMI – Understanding & Calculating Your Fat Free Mass Index & How Much Muscle Mass You Can Build Naturally

FFMI Calculator (2)

What Is FFMI?

FFMI, an abbrievation for fat free mass index is a formula used to calculate the amount of muscle mass an individual is carrying in relation to how tall they are. The fat free mass index calculation isn't often discussed as BMI (body mass index) still remains the mainstream calculation for measuring an individual's height and weight to determine whether they're in good health or not.

There is absoultely no question that FFMI is a far better, more accurate indicator of health and body condition than the BMI measurement.

If you live a sedetary lifestyle and don't perform any resistance training or have any interest in building muscle mass or improving your body composition the BMI calculator will give you a quick snapshot of your health however if you're a gym-goer or an athlete you should not be using or referring to your body mass index (BMI) measurement.

So What's The Problem With BMI?

Body mass index retro infographics poster. Vector illustration.

BMI does not take into account how much lean muscle mass your body is carrying, or the amount of stored body fat you have.
The only two number BMI takes into account before spitting out your score is your height and your weight, this is the exact reason why BMI is completely flawed if you're an athlete or gym-goer.

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A competitive bodybuilder with stacks of muscle mass and barely a few pounds of body fat on his physique will likely score in the BMI range that will class him as at least overweight, if not obese.

While, on the other hand an untrained individual with barely a few pounds of muscle mass and a whole heap of stored body fat will likely be classed as being in the 'healthy' range, even though their excessive amount of stored body fat can put them in the higher risk category for numerous diseases and health problems.

How Much Muscle Mass Can You Build Naturally?

What can the fat free mass index tell us about our potential when it comes to building muscle naturally?

A study performed back in 1995 on a group of top tier athletes (some were known steroid users) was compaired against the competition winners of the 1939 - 1959 Mr  America competition. These circa 1960 Mr America competitors were competing during the pre-steroid error. The conclusion? A fat free mass index around 25 is the upper level for a natural athlete or gym-goer. As in any discipline, there's going to be a select group of outliers, of genetic freaks and the like who will be able to (slightly) exceed this upper limit without chemically enhancing their physique...

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FFMI Study


If 25 is a top tier, elite fat free mass index for a natural athlete how does the average man walking the street stack up? And where are the Mr. Olympia enhanced athletes of today on this scale? Let's take a look...

  • 16 – 17: below average
  •  18 – 19: average
  • 20 - 21: above average
  • 22: excellent
  • 23 – 25: superior
  • 26 – 27: suspicious for a natural athlete, but not impossible
  • 28 – 30: essentially impossible naturally, steroid user

For example, in my current condition at 190lbs and 10% body fat at 6 foot tall my adjusted FFMI is 23.5, placing me in the superior range.
At my current body fat and height to reach a FFMI of 25 (considered the top tier for a natural athlete) I'll need to add an additional 10lbs of muscle mass while maintaining the same body fat level.

I personally see the FFMI calculator to be an extremely realistic calculator of what you can expect to be able to build naturally.
Putting the scales, measurements and all the other methods of measurement aside, when you're reporting a FFMI of 22 or above there'll be no question as to whether you look like you lift or not.

Let's take a look at a few more examples...

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160lbs with 8% body fat at 5 9" = FFMI of 21.7 - above average

180lbs with 15% body fat at 5 11" = FFMI of 21.5 - above average

280lbs with 40% body fat at 6 5" = FFMI of 20.9 - above average

150lbs with 18% body fat at 6 1" = FFMI of 16.8 - below average

200lbs with 10% body fat at 6 0" = FFMI of 24.7 - Top of the superior range

Now, let's give the (inaccurate) BMI calculator a try...

Utilizing my stats, the same ones that I entered into the FFMI calculator, at 6 foot and weighing in at 190lbs I'm considered overweight, falling just outside of the healthy range (capped from 18 - 25).

How Do You Stack Up On The FFMI? Let Me Know In The Comments Below!

Scott J.
Scott J.
I’m SJ. I’m a fitness enthusiast and published author. I transformed my body from a skinny fat 135lbs with 18% body fat to a solid 192lbs at 8% body fat. I became qualified in a field I was passionate about. I founded several online businesses that allow me to pursue ideas and projects in my life that I am passionate about without having to constantly worry about money. I published several eBooks explaining the training and dieting techniques I used to achieve the body I have today. I learnt a plethora of new information on dieting and fitness by reading and applying what I read, to find out what does work and what doesn’t work, because as I’m sure you’ve noticed the health and fitness industry is full of non-sense claims and BS. I found out what was true and what worked for me and applied that knowledge. And you bet I had fun during the whole process.

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