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The RFM formula
Men: RFM = 64 − 20 × (height ÷ waist)
Women: RFM = 76 − 20 × (height ÷ waist)
Use the same units for height and waist. Measure your waist at the belly button, standing, after breathing out.
Examples
| Person | Calculation | RFM |
|---|---|---|
| Man, 175 cm, 85 cm waist | 64 − 20 × (175 ÷ 85) | 22.8% |
| Woman, 165 cm, 80 cm waist | 76 − 20 × (165 ÷ 80) | 34.8% |
How accurate is it?
The researchers built RFM from US national survey data and checked it against body fat measured by DEXA scans. In their study, RFM estimated body fat more accurately than BMI did, and it misclassified fewer people.1 Like any formula, it can be off for individuals.
RFM vs. BMI
RFM uses your waist and gives a body fat percentage, while BMI gives a weight-for-height number.
| What RFM shows | What it doesn't show |
|---|---|
| An estimate of your body fat percentage | Your exact body fat; it can be off for individuals |
| Fat around the stomach, which BMI can't see | Official categories: most guidelines refer to BMI |
| A result from just a tape measure, no scale | Your weight, since the formula doesn't use it |
Frequently asked questions
What is a healthy RFM?
RFM is a body fat estimate, so general body fat ranges apply: see the ranges.
Can I use inches?
Yes. Use inches for both height and waist. The units cancel out.
Sources
This page is for education and is not medical advice. Talk with a healthcare professional about your weight and health.
