Fat Free Mass Index (FFMI) Calculator

Medically reviewed by Gabrielle Kane, RDN, CSP, LD Gabrielle Kane Gabrielle KaneRDN, CSP, LD facebook_iconinsta_icon
Written by , BTech (Biotechnology), Certified Health & Nutrition Life Coach Sindhu Koganti BTech (Biotechnology), Certified Health & Nutrition Life Coach linkedin_icon Experience: 6 years
Edited by , BA (Literature & Psychology), PG Diploma Arshiya Syeda BA (Literature & Psychology), PG Diploma linkedin_icon Experience: 7 years
Fact-checked by , BSc (Life Sciences), Certified Health & Nutrition Life Coach Himanshi Mahajan BSc (Life Sciences), Certified Health & Nutrition Life Coach linkedin_icon Experience: 2 years

Excessive fat in the body is harmful. Keeping track of your body fat content is essential for maintaining a healthy body. However, people often give more importance to measuring their weight instead of the amount of body fat. The irony that can arise here is that a person with less body weight vis-a-vis height can have a greater relative body fat content and vice-versa. Therefore, maintaining balanced body fat levels is essential and associated with a longer, disease-free life. The Fat-Free Mass Index (FFMI) calculator can help you track your body fat content. Keep scrolling to check out the tool and learn more about it.


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What Is Fat-Free Mass Index (FFMI)? Is It Different From BMI?

Fat-free mass index (FFMI) is the measure of the muscle mass a person carries in correlation to their weight and height (1).

Advocates of FFMI consider it better than BMI or body mass index, as it gives a better overview of a person’s physical state. BMI is calculated according to a person’s weight and height and doesn’t take lean muscle mass and body fat into account (2). For instance, people with different weights and heights may have the same BMI even if their body fat levels and muscle mass are different. Higher body fat content will affect a person’s overall health, energy, stamina, immunity, and risk of developing diseases like cardiovascular issues and diabetes (3). Therefore, measuring only BMI does not indicate the overall physical state of a person, as a person with more muscle mass may have a negative BMI and vice versa. This is where the FFMI calculator can help.

FFMI calculator may help you track your fat loss progress and muscle-building process. It is often used by athletes, bodybuilders, and fitness enthusiasts.

What Is The Normal FFMI Range In Men And Women?

The normal FFMI range (in kg/m²) for men is between 15.1 and 16.6 and for women, it’s between 17.1 and 19.7. On the other hand, a low FFMI in men is below 17.4, and in women, it’s below 15.0 (a class=”citation_class” href=” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4684827/” target=”_blank” rel=”follow noopener noreferrer”>4). A high FFMI value indicates more muscle mass with respect to height.

Having a healthy fat-free mass is important for many reasons. Let’s understand this in the next section.

The Importance Of A Healthy Fat-Free Mass (FFM)

Having a high fat-free mass helps in leading a healthy lifestyle and reduces the risks of high blood pressure and developing issues like cardiovascular diseases, type 2 diabetes, and obesity-related depression (1), (5), (6), (7).

Fat-free mass generally includes all components in your body except for fat (also called adipose tissue). It may include internal organs, bones, connective tissues, and different muscles (like skeletal and cardiac muscles) (5). However, when it comes to body composition and weight management, fat-free mass usually refers to muscle mass.

To reap the benefits of weight loss, one should try to decrease the fat mass and improve fat-free mass like muscle and bone. A high body fat percentage is one of the prime reasons for obesity (8).

Our body needs just the right amount of fat to keep it healthy. Athletes usually have low body fat percentage, as a result, they can perform at their peak. Some athletes like linemen (in football) and sumo wrestlers have relatively high body fat percentages but can perform at a high level.

How To Calculate Fat-Free Mass

You can use these simple formulas to calculate fat-free mass:

Fat-Free Mass = weight in kg X (1 – (body fat [%]/ 100)).

To calculate body fat, use this formula:

Body Fat = weight [kg] X (body fat [%] / 100).

FFMI Vs. Normalized FFMI Calculation

In normalized FFMI, the values are slightly modified for a 1.8 m tall person. This calculation is often used for athletes. Here are the equations (9):

FFMI = (fat-free mass in kg) X (height in meters) – 2

Normalized FFMI = FFMI + 6.3 X (1.80 m – height in meters)

You can select the units (like cm, kg, etc.) in the fat-free mass index calculator as per your preferences.

Why Men And Women Have Different FFMI?

Men and women have different body composition. Women have a higher fat percentage in their bodies compared to men. The excess fat is essential for maintaining their menstrual cycle and to support pregnancy. On the other hand, men have more muscle mass and greater bone density than women. Women usually have a greater fat distribution around their hips and thighs. Men commonly accumulate fat around their trunks and abdomen (10). This difference in fat percentage results in different FFMI.

Do Sumo Wrestlers Have More Muscle Mass?

Sumo wrestlers have an excessively high BMI score, based on which they are often categorized as severely obese. However, they have remarkable muscle development, and therefore, they have an excessive fat-free mass and skeletal muscle mass. Hence, their FFMI score is exceptionally high (11), (12).

The FFMI calculator adds depth to your fitness assessment as it provides a clear picture of the muscle mass in your body. Unlike BMI, it considers both muscle and fat composition beyond the usual body mass factor. Understanding FFMI is important as it aids in setting personalized fitness goals and may help you understand how much muscle mass you need to gain. Remember, FFMI is not just for bodybuilders and athletes, but anyone striving for a healthier body composition can benefit from it. So, harness the insights you get from the FFMI calculator to tailor your fitness journey and achieve a well-rounded physique.

Frequently Asked Questions

Is FFM the same as lean body mass?

The terms FFM and LBM are often used interchangeably, but they are not the same. Fat-free mass (FFM) is composed of bone, muscle, vital organs, and extracellular fluid. On the other hand, Lean Body Mass (LBM) also includes lipids contained in cellular membranes. However, this constitutes just a minor portion of overall body weight, accounting for about 3% in men and 5% in women (13).

How does age affect the Fat-Free Mass Index?

The FFMI gradually decreases with age. It happens mainly because of loss of skeletal muscle mass. Moreover, the body composition also changes with age, and women often undergo age-related hormonal changes. All these factors may impact FFMI (14).


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  1. Relationship of Fat Mass Index and Fat Free Mass Index With Body Mass Index and Association With Function Cognition and Sarcopenia in Pre-Frail Older Adults
  2. Body Mass Index (BMI): A Screening Tool Analysis
  3. Percent body fat and chronic disease risk factors in U.S. children and youth
  4. Stratification of fat-free mass index percentiles for body composition based on NHANES III bioelectric impedance data
  5. Effect of fat mass index fat free mass index and body mass index on childhood blood pressure: a cross-sectional study in south China
  6. Associations of changes in fat free mass with risk for type 2 diabetes: Hispanic Community Health Study/Study of Latinos
  7. What is the Importance of Body Composition in Obesity-related Depression?
  8. Optimal Body Fat Percentage Cut-Off Values in Predicting the Obesity-Related Cardiovascular Risk Factors: A Cross-Sectional Cohort Study
  9. Fat-free mass index in users and nonusers of anabolic-androgenic steroids
  10. Sex differences in human adipose tissues – the biology of pear shape
  11. Hierarchical differences in body composition of professional Sumo wrestlers
  12. Comparison Of Normalized Maximum Aerobic Capacity And Body Composition Of Sumo Wrestlers To Athletes In Combat And Other Sports
  13. Lean body mass: the development and validation of prediction equations in healthy adults
  14. Ethnic and age-related fat free mass loss in older Americans: The Third National Health and Nutrition Examination Survey (NHANES III)

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Gabrielle Kane

Gabrielle KaneMS, RDN, CSP, LD

Gabby is a Registered Dietitian Nutritionist with 11 years of experience. She is also the founder of Peak Performance Nutrition LLC in Houston, Texas. She coaches both adults and children to their peak health using the power of sustainable lifestyle change. In addition to a BA in Nutrition and Psychology from Case Western Reserve University, she also has a Master's...read full bio