FFMI (Fat-Free Mass Index) Calculator

The FFMI (Fat-Free Mass Index) Calculator estimates fat-free mass index based on your body fat percentage, weight, and height. To Calculate your FFMI, just select a measuring system, enter your height and weight and finally enter the percentage of your body fat. Then click the "Calculate" button to generate the result.

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Fat-Free Mass Index Calculator: If converting fat-free mass, weight, and height into the fat-free mass index is difficult for you and you are unfamiliar with the order of operations, you may use the online Fat-Free Mass Index (FFMI) Calculator to assist you. In the following sections, you will learn about the manual approach to calculate FFMI and solved example. Get Fat Free Mass Index definition and Fat Free Mass Scale deatils.

What is the Fat-Free Mass Index?

Fat-Free Mass Index or FFMI is a proposed method for assessing body composition in individuals who have a similar body composition but differ in height in order to identify those with malnutrition, wasting, or high muscle mass

How is FFMI Different from BMI?

FFMI corresponds conceptually to Body Mass Index (BMI). However, instead of measuring body mass in relation to height, it measures lean muscle mass in relation to a person's height.

It provides information about someone's condition and state of health as well as the amount of muscle mass in relation to their height and weight. Although not as popular as BMI, the FFMI is more precise than BMI.

Fat-Free Mass Scale

This chart is an indication of a person’s FFMI & its meaning related to the health of a person.

range of FFMI 


below 18

Less than average

18 - 20


20 - 22

More than average

22 - 23


23 - 26

Very good

26 - 28

Likely use of steroid

more than 28

Most likely use of Steroid

Here, are points to consider

  • A range of FFMI of 26-27.9 may indicate likely use of steroids, but it can still able to achieve without taking steroids.
  • A range of FFMI of more than 28 is mostly impossible without taking steroids.

FFMI (Fat Free Mass Index) Formulas

Fat-Free Mass Index (FFMI): 

FFMI [kg/m2] = FFM [kg] / (height [m])2

Normalized Fat-Free Mass Index: 

Normalized FFMI [kg/m2] = FFM [kg] / (height [m])2 + 6.1 × (1.8 − height [m])

Fat-Free Mass (FFM):

 FFM [kg] = weight [kg] × (1 − (body fat percentage / 100))

How to calculate fat mass and fat-free mass Manually?

  1. To calculate FFMI, we need to know the weight & height of a person. We also need body fat percentage.
  2. According to the units we use (imperial or metric), we use the formula to calculate FFMI.
  3. After calculating the results we can check the Fat-Free Mass Scale to see the score & its remarks to check the health of a person.

Solved Example on Fat-free Mass Range Calculation


What is the Fat-Free Mass Index of a person whose height is 180cm, weight is 85kg & body fat percentage is 15? 


Here, we need to see the formula for FFMI first.

FFMI = FFM / (height)2

Also the formula for Fat-Free mass is

 FFM = weight × (1 − (body fat percentage / 100))

We know that height is 180cm, weight is 85kg & body fat is 15%

So after putting the above values in both equations, we get

FFMI = 22.29 

FFM = 72.25 kg

So, according to the Fat-Free Mass Scale chart given above, we can say that this person's overall health is “Very good”.

Begin by using a couple more calculators, and then go to Arithmetic Calculators to calculate other health-related factors.

FAQs on FFMI (Fat-Free Mass Index) Calculator

1. What is a good FFMI?

FFMI more than 20 for men and higher than 17 for women is considered desirable. 

2. How accurate is FFMI?

FFMI is usually considered the best predictor of the portion of total lean muscle mass that a person could potentially develop. It is believed to be an incredibly accurate indicator for testing whether a person is taking steroids or not.

3. What should my fat-free mass be?

A healthy percentage of lean mass is 68 to 80 % for women while 78 to 90% for men.

4. What does adjusted FFMI mean?

The adjusted FFMI score range from 21 to 24 suggests above-average muscle mass, 19-20 expresses normal muscle mass and under 19 indicates low muscle mass.