Estimate your body fat percentage from your height and waist, then see how it compares with the obesity cut-off the RFM’s authors proposed for your sex.
Example: Male, 5 ft 10 in, waist 34 in
22.8%body fat
Your estimate is under 30%, the cut-off the RFM authors proposed for obesity in men.
The authors chose the cut-offs where RFM best separated people by risk of death over about 8 years of follow-up in a US national survey. Enter your own numbers above to replace this example.
The tick is the obesity cut-off for men.
| Obesity cut-off (Woolcott and Bergman 2020) | RFM |
|---|---|
| Your RFM | 22.8% |
| Obesity for men | 30% or more |
- Next stepWaist to height ratio calculatorThe same two measurements against the NICE health risk bands.
Formula: RFM = 64 - 20 x height / waist (men). RFM estimates body fat; it does not measure it.
Sources: Woolcott and Bergman 2018 (Sci Rep); Woolcott and Bergman 2020 (Int J Obes)
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)
- 64 – 42.42 = 21.58
- 21.6% body fat (the calculator rounds to one decimal)
The man in the example has an RFM of 21.6%, under the 30% obesity cut-off for men.
How to read your result: Woolcott and Bergman, who created the RFM formula, proposed cut-offs of 30% for men and 40% for women in 2020 to diagnose obesity. They picked the cut-offs where RFM best separated people by risk of death over about eight years of follow-up in a US national survey. The calculator tells you whether your result is under the cut-off for your sex or at or over it.
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.
Related Calculators:
- BMI Calculator
- Reverse BMI Calculator
- Body Fat YMCA Calculator
- 7 Skinfold Body Fat Calculator
- Body Fat Skinfold Calculator
- 4 Skinfold Body Fat Calculator
- 3 Skinfold Body Fat Calculator
- Body Fat US Navy Calculator
- TDEE Calculator
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.
