FFMI Calculator

A quantitative test to see how muscular you are.

By: Jeremy Fox, CNC, CPTUpdated: June 22, 2022

FFMI (fat free mass index) is a formula to quantify muscle development based on your height, weight, and body fat. The FFMI calculator gives you a numeric value to help you measure your physique and see how it compares to other people.

ffmi calculator

ffmi calculator gym persona

Please note, gym persona is intended to be a fun way to assess fitness level… don’t take it too personally!

When you input your numbers into the FFMI calculator, you get two unitless numbers. The first is FFMI and the second is FFMI adjusted for your height.

I’ve also included qualitative descriptions of your lean mass and body fat levels so it makes more sense. Finally, you get a “gym persona” that best describes your current fitness level.

To better understand your score, I suggest you skim through some of the sections below covering everything you need to know about FFMI.

What Is FFMI?

FFMI (fat free mass index) is a measure of muscularity based on gender, height, weight, and body fat percentage. This numeric value quantifies your lean mass compared to other people in your demographic.

More importantly, you can use FFMI to determine your ideal weight and adjust your diet/workout routine to hit a specific target.

FFMI Scale for Men

For men, the FFMI scale generally ranges from 15 to 25. On this scale, anything under 18 is skinny, while 18-20 is average.

Continuing the scale, an FFMI of 20-21 is athletic, and 21-23 is very well built. Finally, an FFMI over 23 is considered extremely muscular for men.

Table 1. FFMI Scale Men

<18 Skinny
18-20 Average
20-21 Athletic
21-23 Very Well Built
>23 Extremely Muscular
FFMI Category

FFMI Scale For Women

Generally, building muscle is more challenging for women, so the scale ranges from 12 to 22. Any score under 15 is considered skinny, while 15-16.5 is average for females.

An FFMI in the range of 16.5-18 is athletic, and 18-20 is very well built. At the top end of the scale, women with a score over 20 are considered extremely muscular.

Table 2. FFMI Scale Women

<15 Skinny
15-16.5 Average
16.5-18 Athletic
18-20 Very Well Built
>20 Extremely Muscular
FFMI Category

FFMI Natural Limit

For men, an FFMI over 25 is considered unlikely without the use of steroids. While anything over 22 is difficult to attain for women without performance enhancers.

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

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

Still, it is possible to exceed 25 naturally with good genetics and years of hard work.

Related: Is Chris Bumstead Natural?

FFMI Percentiles

When trying to see if you’re above or below average, it’s helpful to look at a large population. For example, 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 most people fall on the FFMI scale and where you stand in comparison.

ffmi chart men

Table 3. FFMI Percentile Men

Top 5% Above 22.5
Top 10% Above 21.5
Top 25% Above 20.5
Top 50% Above 19.5
Percentile FFMI
ffmi chart women

Table 4. FFMI Percentile Women

Top 5% Above 18.5
Top 10% Above 17.5
Top 25% Above 16.5
Top 50% Above 15.5
Percentile FFMI

FFMI by Height & Weight

Weight distribution is different for taller and shorter people. So FFMI is normalized to average height (5’11” for men and 5’4″ for women.) You’ll see your standard and adjusted 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.

To illustrate, the graphs below show the FFMI ranges at different heights for males and females.

Related: Bradley Martyn Height, Weight, FFMI

ffmi scale men
ffmi scale women

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

First, 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”.

How to Improve FFMI

It’s important to consider body fat and 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 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 category.

7 Simple Steps To Get Shredded

Table 5. Male Body Fat Categories

<10% Very Lean
10-17% Athletic
17-24% Average
24-30% Overweight
>30% Obese
Body Fat Category

Table 6. Female Body Fat Categories

<18% Very Lean
18-25% Athletic
25-32% Average
32-39% Overweight
>39% Obese
Body Fat Category

The “Gym Persona” matrix makes it easier 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 to move down.

Bulk vs Cut: How to Choose the Right Fitness Goal

ffmi calculator gym persona


Now you have a pretty good idea about what FFMI is and how it’s used. But here are some quick answers to other common questions surrounding FFMI.

How is FFMI calculated?

The calculation for FFMI is lean mass/height2. Where lean mass is weight-(weight*body fat percentage/100).

This FFMI calculator also considers your gender to give you a relative score.

What is a good FFMI?

For men, the average FFMI is 19.5. But you should shoot for an FFMI of at least 21.5 if you want to stand out at the gym.

An average FFMI for women is 15.5. So an FFMI of 17.5 would likely get you noticed.

What is a suspicious FFMI?

An FFMI of 26-28 should draw suspicion of steroid use among male bodybuilders. While an FFMI over 28 is almost certainly the result of steroids.

Keep in mind that FFMI is not a definitive cutoff. So it would be best if you didn’t blast people on social media for being “fake natty” without knowing more about their background.

Are FFMI and BMI the same thing?

Both FFMI (fat free mass index) and BMI (body mass index) categorize people based on height and weight. But they are not at all the same thing!

BMI only accounts for your total body weight, whereas FFMI considers your body composition. Therefore, FFMI is generally more accurate for active people and is a better tool for finding your ideal weight.

Is FFMI a good measure?

FFMI can be a helpful tool for assessing your current fitness level and setting future goals. And it is better than BMI for people who lift weights.

However, it would be best to consider multiple measurements and metrics to achieve optimal health and fitness.

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FFMI is a valuable tool for men and women to assess their current fitness levels. 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.

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

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

Body Fat Percentage Calculator

Knowing your body fat percentage is a major factor in finding your FFMI. So I suggest you try my free body fat percentage calculator to make sure you got the right FFMI score.

You can calculate your body fat percentage more accurately using a skin fold test or simple body circumference measurements. Click below to try it!

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