RFM Calculator
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Relative fat mass estimates body fat percentage from two tape measurements: RFM = 64 − 20 × (height ÷ waist) for men and 76 − 20 × (height ÷ waist) for women. In its 2018 study it matched DEXA body fat better than BMI did.
| RFM | 37.2% |
| Height ÷ waist | 1.941 |
| Suggested obesity cutoff | 40% (women) |
| Waist-to-height ratio | 0.515 (0.5 or more: higher risk) |
Show steps
- RFM = 76 − 20 × (height ÷ waist) (Woolcott and Bergman, 2018), using the same units for both.
- = 76 − 20 × (165 ÷ 85) = 37.2%.
How to measure
Measure the waist at the level of the top of your hip bones (iliac crest), after breathing out. Use the same unit for height and waist.
Cutoffs
The study authors suggested RFM of 30% or more for men and 40% or more for women as indicating obesity.
Why ratios work
Waist relative to height captures belly fat, which BMI misses: two people with the same BMI can have very different waists.
RFM Calculator quiz: 10 questions
Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.
Quiz complete
Frequently asked questions
Is RFM more accurate than BMI?
In its validation study it predicted DEXA body fat better than BMI.
Where exactly do I measure the waist?
At the top of the hip bones.
What is a healthy RFM?
Below about 30% for men and 40% for women by the authors' cutoffs; lower is generally better.
Does it work for children?
It was developed for adults.
Can I use inches?
Yes.
Sources
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