RFM Calculator (Relative Fat Mass)

RFM Calculator

With only two body measures – height and waist circumference – our RFM calculator (or Relative Fat Mass calculator) calculates body fat mass. This calculation is more precise than the widely used body mass index (BMI), which frequently misclassifies obesity.

Do you want to know how to figure out how much fat you have? To learn more about the relative fat mass index, read the article below!

Body fat mass – an essential part of the human body

Body fat (also known as adipose tissue) is an important part of the human body. Its main role is to store energy, but it also has other important duties including protecting internal organs and manufacturing hormones (e.g., leptin).

The proportion of body fat in humans varies depending on their age and gender. Due to reproductive and hormonal processes, women have a higher body fat percentage than males, and elderly adults have a higher body fat %.

How to calculate your fat mass?

Relative fat mass index and relative fat mass chart

Our RFM calculator uses equations created by experts from the Sports Spectacular Diabetes and Obesity Wellness and Research Center in 2018 to assess body fat mass percentage (Cedars-Sinai Medical Center, USA). The formula is different for men and women, and it just requires two measurements: height and waist circumference.

The following are the equations:

  • MEN:

RFM = 64 - (20 * height / WC)

  • WOMEN:

RFM = 76 - (20 * height /WC)


RFM – relative fat mass index, expressed in %;

height – expressed in cm; and

WC – waist circumference, expressed in cm.

When used to determine body fat mass, this equation is based on the height-to-waist ratio and is more accurate than BMI. The explanation of the data may be found in the relative fat mass chart below:

InterpretationFat level men (%)Fat level women (%)
Extremely low level of fat<2<10
Essential fat2 – 510 – 13
Athletes6 – 1314 – 20
Fitness14 – 1721 – 24
Average18 – 2425 – 31

RFM calculator – a practical example

Let’s look at a real-life example of how to determine your fat mass. Kathy, who is 170 cm tall and has a waist circumference of 72 cm, will have her relative fat mass calculated. If you’re measuring in inches, don’t panic; the relative fat mass calculator will convert them to centimeters for you.

  1. We will be using the relative fat mass equation for females:

RFM = 76 - (20 * height / WC)

  1. Fill in the necessary information. After doing so, the equation will look like this:

RFM = 76 - (20 * 170 / 72)

  1. We’re almost there! There is just an easy calculation left.

RFM = 76 - (20 * 2.36)

RFM = 76 - 47.2

RFM = 28.8

Kathy has a relative fat mass of 28.8 percent. This is an average result, according to the relative fat mass chart in the RFM calculator. Kathy, you did an excellent job!

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