22.8
%
—
24.5
kg/m²
20.1
%
22.8
%
—
24.5
kg/m²
20.1
%
The Relative Fat Mass (RFM) is a novel body fat estimation metric developed by Woolcott and Bergman in 2018, published in the journal Scientific Reports (Nature). It was created through analysis of over 12,000 participants from the National Health and Nutrition Examination Survey (NHANES) and represents a significant advancement in simple, non-invasive body fat estimation. RFM uses only height and waist circumference to produce a body fat percentage estimate that correlates with DEXA-measured body fat better than BMI, waist circumference alone, or waist-to-height ratio.
The formula is remarkably simple: for men, RFM = 64 - 20 x (height/waist); for women, RFM = 76 - 20 x (height/waist). The sex-specific constants account for the fundamental difference in body fat between men and women (women naturally carry approximately 12% more body fat). The height-to-waist ratio captures the balance between body frame size and central adiposity. What makes RFM particularly elegant is that it does not require weight at all, yet provides a body fat estimate that rivals more complex multi-variable equations.
In the validation study, RFM was tested against whole-body DEXA scanning in over 3,000 subjects. The concordance correlation coefficient with DEXA was 0.85 for men and 0.81 for women, significantly outperforming BMI (which had concordance of 0.59 for men and 0.68 for women). RFM also showed less bias across the range of body fat percentages, whereas BMI-based estimates become progressively less accurate at higher fat levels.
Several follow-up studies have confirmed RFM's clinical utility. Research published in the Journal of the American Heart Association found that RFM was a better predictor of cardiovascular and metabolic outcomes than BMI, including diabetes risk, hypertension, dyslipidemia, and metabolic syndrome. A 2020 study in the European Journal of Clinical Nutrition showed that RFM predicted type 2 diabetes risk more accurately than BMI in a large prospective cohort of over 50,000 adults.
This calculator provides your RFM with a body fat category classification, along with BMI and BMI-derived body fat percentage for comparison. The comparison is valuable because it highlights cases where BMI and RFM disagree, which often signals that BMI is giving misleading information about your true body fat level. This is common in individuals with high muscle mass (where BMI overestimates fat) or with central obesity at normal weight (where BMI underestimates fat). RFM is recommended as a practical first-line screening tool that requires only a tape measure and a height measurement.
The RFM formulas are: Men: RFM = 64 - 20 x (height / waist). Women: RFM = 76 - 20 x (height / waist). Height and waist in the same units (cm). The result directly approximates body fat percentage. Higher height-to-waist ratio means lower body fat. The sex-specific constants reflect the ~12% higher essential body fat in women. Categories are based on standard body fat classifications.
RFM directly estimates body fat percentage. For men: below 10% is athletic, 10-18% is fitness, 18-25% is average, above 25% is obese. For women: below 18% is athletic, 18-25% is fitness, 25-32% is average, above 32% is obese. Compare with the BMI-derived body fat estimate: when they agree, confidence is high; when they diverge, RFM is typically more accurate (validated against DEXA).
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RFM estimates 20.1% body fat, closely matching the BMI-derived 20.3%. Both indicate average body fat for a male.
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RFM estimates 28.0% body fat vs BMI-derived 26.4%. Both in the average range for women, with reasonable agreement.
RFM is a body fat estimation formula using only height and waist circumference. Developed in 2018, it produces a body fat percentage that correlates better with DEXA scanning than BMI does.
Yes, for estimating body fat percentage. Studies show RFM has a concordance correlation of 0.81-0.85 with DEXA, compared to 0.59-0.68 for BMI. RFM also better predicts cardiovascular and metabolic disease risk.
RFM uses the height-to-waist ratio, which captures the relationship between body frame size and central fat accumulation. This ratio, combined with sex-specific constants, provides sufficient information to estimate total body fat percentage.
Measure height without shoes on a flat surface. Measure waist at the narrowest point of the torso or at the navel, standing upright, breathing normally. Use a flexible tape measure snug against the skin.
RFM works reasonably well for athletes because it uses waist circumference rather than weight. A muscular athlete with a large frame but small waist will get a lower (more accurate) body fat estimate from RFM than from BMI.
The original study used NHANES data, which includes diverse US populations. Subsequent validation studies have confirmed RFM's accuracy in European, Asian, and Latin American populations, though slight variations in accuracy exist.
Both estimate body fat without weight, but they use different measurements. BAI uses hip circumference and height; RFM uses waist circumference and height. RFM generally shows better agreement with DEXA-measured body fat.
RFM uses waist circumference, which reflects both subcutaneous and visceral abdominal fat. While it cannot distinguish between the two types, individuals with high RFM are likely to have elevated visceral fat levels.
Monthly tracking is sufficient for most people. RFM changes reflect waist circumference changes, which respond to diet and exercise over weeks to months. For consistency, measure at the same time of day under the same conditions.
RFM has been proposed as a superior alternative to BMI for clinical screening. While it performs better at estimating body fat and predicting metabolic outcomes, BMI remains the most widely used metric. Using both provides the most complete picture.
Roboculator Team
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