FFMI Calculator: Calculate Your Muscle Mass

An FFMI calculator is a helpful tool to help estimate how much lean mass you possess based on your height. This can help you understand how muscular you are, track your lean mass and provide extra insight into your physique.

The BMI calculates your body weight in relation to your height, however it doesn’t take muscle and fat into account. This can be a limiting factor for you if you take part in any form of strength training, body building or muscle building. Two people could be the same height and weight but have very different body compositions.

The FFMI takes into account fat free mass. Fat free mass refers to anything in your body that isn’t fat. This includes muscles, bones, organs and water.

The FFMI calculator will calculate your Fat Free Mass Index based on your weight, height and estimated body fat percentage. The calculator can also give you an adjusted FFMI based on your height.

Whether you’re a beginner or a seasoned gym goer, this calculator can give you some extra information about your body.

How to Use the FFMI Calculator

The calculator is very easy to use and you’ll only need a few simple measurements.

To use the calculator follow the steps below;

• Enter your weight – Enter your current body weight in either kg or lbs.
• Enter your height – Enter your height in either feet/inches or cm.
• Enter your body fat percentage – Enter your estimated body fat percentage. For example if your body fat percentage is 18% enter 18.
• Units – Select the correct weight and height units.
• Calculate your FFMI – Press the calculate button.
• View your results – The calculator will show your estimated fat free mass,

FFMI and possibly your adjusted FFMI.

Try to use up-to-date body measurements and an accurate estimation of body fat for more accurate results.

FFMI Calculator Formula

The formula for calculating the Fat Free Mass Index looks at how much lean mass you have based on your height squared.

There are two main formulas;

Calculating Fat Free Mass

Firstly calculate your fat free mass by subtracting your body fat mass from your total weight.

FFM = Weight x (1 – Body Fat%)

For example if your weight was 180lbs and your body fat percentage was 20% then;
FFM = 180 x (1-0.20)
FFM = 144lbs

Therefore your estimated fat free mass is 144lbs.

Calculating Fat Free Mass Index

The standard formula for calculating your FFMI is;

FFMI = FFM (kg) / Height (m) 2
Where;

FFM – Fat Free Mass in kg.

Height – Height measured in metres.

FFMI – Fat Free Mass Index.

Calculating Adjusted FFMI

You can calculate an adjusted FFMI based on your height to compare individuals.

One widely used formula is;

Adjusted FFMI = FFMI + 6.1 x (1.8 - Height)

Remember to enter your height in metres.

This uses 1.8m as a standard height and is an estimate of how muscular someone can be.

Example FFMI Calculation

Below is an example of how to calculate your Fat Free Mass Index.

Let’s say;

Measurement Value

Body Weight 180lbs

Height 5’10”

Body Fat % 20%

Weight (kg) 81.65

Height (m) 1.778

Calculate Fat Free Mass

FFM = 81.65 x (1-0.20)

FFM = 65.32kg

Calculate FFMI

FFMI = 65.32 / 1.778 2

FFMI = 65.32 / 3.1613

FFMI = 20.66

Calculate Adjusted FFMI

Adjusted FFMI = 20.66 + 6.1 (1.8 - 1.778)

Adjusted FFMI = ~20.79

Example Results

The individuals standard FFMI would be approximately 20.66 and their adjusted FFMI would be around 20.79.

This gives an indication of how much lean mass they have based on their height.

Understanding your FFMI

Your FFMI will give you an indication of how muscular you are based on your height.

Below are some general guidelines for men;

FFMI Score General Meaning

<18 Less Muscular

18-20 Average Muscular

20-22 More than average Muscular

22-23 High Muscular

23-25 Very High Muscular

>25 Extremely High Muscular

These are just a general indication and not a standard medical or fitness guideline.

Women will also generally have a lower FFMI score due to the average body composition and distribution of fat free mass. Don’t use the male guidelines for females.

Also take into consideration your experience, body fat percentage, age, genetics and general health.

Having a higher FFMI doesn’t necessarily mean you’re fitter or healthier. The aim is to have a healthy and sustainable body composition.

Factors That Affect Your FFMI

There are a number of factors that can affect your FFMI.
Body Fat %

This is one of the most important factors to get right. If your body fat percentage is incorrect this can greatly affect your FFMI.

Muscle Mass

Those who take part in resistance training and strength exercises will have more lean mass which can increase your FFMI.

Height

Your height will directly affect your FFMI as it is divided by your height squared.

Genetics

Genetics will affect how muscular you can become, body shape, distribution of muscle and natural body composition differences.

Age

As we age our muscle mass can change. Older adults may lose muscle due to age whereas younger adults may still be building their muscular strength and size.

Nutrition & Protein

Consuming enough calories and protein will help build muscle.
Experience

Those who have regular experience of resistance training may have a higher FFMI than those who don’t regularly do strength exercises.

Hydration

Your body water will contribute to your fat free mass. Temporary changes in body water levels can affect your body composition.

Benefits of Using an FFMI Calculator

Below are some benefits of using an FFMI calculator.

• Tracking Muscle Mass – Track how your lean mass is changing as you progress through your strength training.
• Understanding Body Composition – Understand how muscular you are based on your body composition.
• Setting Fitness Goals – Set realistic goals for your body composition.
• Tracking Weight Loss – See if your body weight is changing along with your estimated fat free mass.
• Body Building – Use the FFMI as another measurement to track your physique.
• Track Progress – Regularly calculate your FFMI to see how your lean mass is changing based on your height.
• Understand Training Results – Understand how resistance training, nutrition and recovery may be affecting your body composition.

For the most accurate results try to use other indicators such as waist size, strength, body weight trends and body fat percentage.

Accuracy, Assumptions & Limitations

The FFMI calculator will only give you an indication and not an exact figure of how muscular you are. The accuracy depends greatly on how accurate your information is.

The most important thing to note is your body fat %. If your body fat % is inaccurate then your fat free mass and FFMI will be inaccurate.

There are many ways to measure body composition such as skin fold calipers, bioelectrical impedance analysis (BIA) and DEXA scans. All of these can give different results and even the most advanced methods have limitations.

Fat free mass includes more than just muscle. It includes bones, organs, connective tissue and water. Therefore FFMI shouldn’t be seen as a direct measurement of your skeletal muscle mass.

The adjusted FFMI also has a mathematical formula for height. It doesn’t take all differences in body shape, genetics and physicality into account.
The commonly referenced FFMI ranges aren’t a diagnostic measure. Don’t use them to determine if someone is healthy, naturally muscular or using performance enhancing substances.

Try to use the same method of measuring body composition each time for more accurate tracking. Try to use your FFMI in conjunction with other fitness and health indicators.

If you have any specific concerns regarding your body composition or health then please consult a qualified healthcare professional/registered dietitian.

FAQs

What is a good FFMI?

A good FFMI will depend on your sex, age, genetics and experience. For males aged 20-22 is often seen as above average. Between 22-25 generally means you’re more muscular. These are just general guidelines and not a health indicator.

What is the difference between FFMI and BMI?

BMI calculates your total body weight in relation to your height. Whereas FFMI calculates your fat free mass based on your height. This can give you more information on how muscular you are, especially if you regularly take part in strength training.

How do I calculate FFMI manually?

To calculate your FFMI manually take your body weight and multiply by 1 minus your body fat %. Then convert your fat free mass into kg, convert your height into metres. Square your height and divide your fat free mass by your height squared.

Is an FFMI of 25 high?

Yes. An FFMI of around 25 is generally seen as a high level of muscularity for males. However this is just a descriptive guideline and not a universal limit of how muscular you can become naturally. Take into consideration your body composition, genetics and individual differences.

Can women use an FFMI calculator?

Yes. Women can use an FFMI calculator to calculate their fat free mass based on their height. However female results should be interpreted using the correct guidelines for females.