This online RFM Calculator (or Relative Fat Mass Calculator) estimates the body fat mass percentage using two body measurements – height and waist size (waist circumference). To calculate the RFM value choose the appropriate units of measurement and specify the height and waist size either using the sliders or by entering the data into the calculator fields, then specify the gender.
Why Knowing Your Body Fat Mass Matters
Body fat mass is a key indicator of health. Unlike body weight alone, fat mass offers deeper insights into an individual’s physical condition. Maintaining an appropriate level of body fat is essential because both excess fat and lack of fat can have serious health consequences.
Elevated fat levels are associated with a greater risk of cardiovascular disease, type 2 diabetes, hypertension, stroke, and some types of cancer. Obesity can also contribute to joint problems, respiratory issues, and psychological disorders such as depression.
Conversely, having low body fat can impair body functions. Essential fat is necessary for hormone production, vitamin absorption, and temperature regulation. Very low body fat percentages can lead to fertility problems, weakened immunity, and organ damage.
Understanding your body fat percentage helps in setting realistic fitness goals, tracking progress, and making informed decisions about diet and exercise routines.
How Body Fat Mass Is Calculated
Body fat mass can be measured or estimated using various methods, each differing in complexity, accuracy, and accessibility.
Bioelectrical Impedance Analysis (BIA). Commonly used in home scales and gyms, this method sends a small electrical current through the body and estimates fat content based on resistance levels.
Dual-Energy X-ray Absorptiometry (DEXA). Considered a gold standard, DEXA scans provide highly accurate fat measurements along with bone density and lean mass assessments.
Skinfold Calipers. This method involves measuring the thickness of skinfolds at specific body sites and using formulas to estimate body fat percentage.
Hydrostatic Weighing. Also known as underwater weighing, this technique calculates body density by measuring body weight in and out of water.
Body Mass Index (BMI). Although not a direct measure of fat, BMI is a simple and widely used tool that categorizes individuals based on height and weight. However, it does not distinguish between muscle and fat, making it less precise for many people.
Relative Fat Mass (RFM) offers a new, simple way to estimate body fat without expensive equipment or professional measurements.
What Is Relative Fat Mass (RFM)?
Relative Fat Mass (RFM) is a concept developed by researchers at Cedars-Sinai Medical Center in 2018 as an alternative to BMI. It uses only height and waist circumference, making it accessible and easy to calculate.
The formula for RFM is gender specific:
Height and waist size (waist circumference) should be measured in the same units, such as inches or centimeters. When using our RFM Calculator, you have no chance of getting confused with units of length.
RFM was designed to provide a closer approximation of body fat percentage than BMI. Waist circumference is a strong indicator of abdominal fat, which is more strongly linked to health risks than overall weight.
How to Interpret RFM Results
RFM values estimate body fat percentage, with healthy ranges typically around 6–24% for men and 14–31% for women. Higher RFM suggests greater body fat and potential health risks, while very low values may indicate underfat conditions. Since RFM is only an estimate, it should be considered alongside other health measures for a full evaluation.
The relative fat mass results can be interpreted in line with the cut-offs established by the American Council on Exercise:
Advantages and Disadvantages of Using RFM
Relative Fat Mass (RFM) offers a simple, accessible, and gender-specific method for estimating body fat using only height and waist circumference. It often provides better accuracy than BMI, especially in accounting for abdominal fat.
However, RFM is still an estimate and can be affected by errors in waist measurement or variations in body composition, such as in very muscular individuals. It also does not distinguish between types of fat and has limited validation across all populations, meaning it should be used as a general guide rather than a definitive health assessment.
Related calculators
Check out our other health calculators such as Body Fat Calculator or Lean Body Mass Calculator.
Disclaimer. Please remember that this calculator is only one of many ways to assess your body fat mass. In case of any concerns about your health, please consult your physician to address your specific situation.