Relative Fat Mass (RFM) Calculator

The relative fat mass (RFM) calculator is a simple online tool that provides a more accurate estimate of body fat mass compared to body mass index (BMI).

Written by Matthew Magnante

Last Updated onJune 9, 2022

What’s your body fat category – athlete, fitness, average, or obese? Find your body fat percentage estimate with the relative fat mass tool.

ImperialMetric

MaleFemale

Height

Height in Feet

Height in Inches

Waist CircumferenceWaist in Inches

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The relative fat mass (RFM) calculator estimates body fat percentage based on a formula that measures the ratio of your height and waist circumference. Research has shown that RFM equations are more accurate than the body mass index (BMI) for predicting body fat mass and health status (1).

Learn more about this helpful online health tool below.

How The RFM Calculator Estimates Body Fat Percentage

The RFM body fat measurement method was developed by researchers at the Cedars-Sinai Diabetes and Obesity Research Institute. It was designed to provide a more accurate approximation of body fat mass compared to the basic Body Mass Index (BMI) formula.

RFM formulas for men and women

RFM calculator uses a separate formula for men and women due to the biological differences between genders that plays a important role in proper classification of body fat status.

We ve included the formulas for both men and women below.

RFM for adult males = 64 – 20 x (Height / Waist circumference)
RFM for adult females = 76 – 20 x (Height / Waist circumference)

If you want to check the accuracy of the RFM calculator, you can use the above formulas to manually calculate your body fat percentage.

So, for example, if you’re a five foot, ten-inch tall male with a 33-inch waist, you would input the details and perform the calculations as follows.

64 – 20 x (Height / Waist circumference)
64 – 20 x (70 inches/33 inches)
21.57 rounded
22% body fat

The individual used in the example has 22% body fat.

According to the American Council on Exercise, the relative fat mass result can also be interpreted as follows:

Classification	Males (% fat)	Females (% fat)
Essential fat	2-5%	10-13%
Athletes	6-13%	14-20%
Fitness	14-17%	21-24%
Average	18-24%	25-31%
Obese	25% and higher	32% and higher

Note: Woolcott and Bergman (2020) propose RFM cut-offs of 40% for females and 30% for males to diagnose obesity and higher mortality risk.

Taking your height measurement

Most people have an idea of their height although it’s common to under or overestimate. You want to take your height measurement with shoes off, feet together, and standing close to a wall. There are may resources on the internet that can help you to get the most accurate reading.

How to measure your waist circumference

To get the most accurate body fat percentage estimation, it’s very important that you understand how to take a correct waist measurement. We’ve provided instructions to ensure you get a proper reading of your waist circumference.

Note: We recommend having someone take your measurement if possible. Although, it’s certainly not required.

Grab a cloth tape measurer or similar and make sure it’s not wrinkled before taking the measurement.
Stand up straight and wrap the tape around the part of your stomach above the hip bones and below the ribs. Make sure the tape is flat against your skin and even from front to back.
Breathe out normally and record the measurement.

Why Should You Know Your Body Fat Percentage?

Your specific reason for calculating your body fat percentage may be different from the next person; however, the end result applies to everyone, whether you have too much body fat or too little. The RFM calculator is a tool which helps you to make adjustments to your body composition effectively.