Relative Fat Mass (RFM) Calculator
A body-fat estimate from just two tape measurements — no scale, no calipers, no skinfold math.
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Your results
An estimate, not a measurement — informational only, not medical advice.
How to use this calculator
Enter your height and waist circumference in the same unit, select your sex, and the calculator instantly estimates your body fat percentage with the Relative Fat Mass formula.
Example: a man who is 70 inches tall with a 34-inch waist gets 64 − 20 × (70 ÷ 34) = 64 − 41.2 = 22.8% RFM.
How it works
The RFM formula, published in 2018: men: 64 − 20 × (height ÷ waist); women: 76 − 20 × (height ÷ waist), with height and waist in the same unit. It needs no scale or calipers — just two tape measurements.
RFM estimates whole-body fat percentage and has been shown to track DEXA scans better than BMI for many adults. Still, it is an estimate, not a measurement: the result here is informational only and is not medical advice.
Frequently asked questions
What is Relative Fat Mass?
A 2018 formula that estimates whole-body fat percentage from your height-to-waist ratio and sex — simpler than skinfold or Navy methods, since it needs only two tape measurements.
How accurate is RFM?
Studies found RFM tracks DEXA scans better than BMI for many adults, but it is still an estimate, not a direct measurement. Individual results can vary.
What units can I use?
Any — inches or centimeters — as long as height and waist use the same unit, because the formula works on the ratio of the two.
What is a healthy RFM?
Roughly 18-24% for men and 28-34% for women is commonly cited as healthy; athletes typically run lower. This is general information, not medical advice.