How this calculator works
Woolcott and Bergman derived RFM using adult NHANES measurements and DXA estimates. Height and waist use matching units. The equation has a sex-specific intercept and is a population estimate, not an individual fat measurement. The waist site is at the top of the iliac crest. This page does not apply the adult equation to children or pregnancy. The result is an estimate for information only and is not medical advice.
Formula
RFM (%) = 64 - 20 x height/waist + 12 x sex, with sex = 0 for the male equation and 1 for the female equation.
Worked example
For a male 180 cm tall with a 90 cm waist, RFM = 64 - 40 = 24%. The female equation with the same measurements gives 36%.
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Frequently asked questions
Why are the equations different?
The sex term was fitted in the original development data. It is part of that particular empirical model.
Can I calculate waist from a desired RFM?
The inverse mode solves the equation. The result is not a recommended waist size or a prediction of how weight change affects it.
Can I enter inches?
Yes. The unit engine converts each measurement before forming the ratio.