Relative Fat Mass Calculator
Estimate body fat percentage from just your height and waist with the Relative Fat Mass (RFM) formula.
About the Relative Fat Mass Calculator
Relative Fat Mass was developed by Woolcott and Bergman (Cedars-Sinai, 2018) from US NHANES data and validated against DXA scans. It needs only height and waist circumference measured at the navel, and in that study estimated body fat more accurately than BMI. Healthy ranges for body fat are roughly 8–20% for men and 21–33% for women, varying with age.
The formula
Men: RFM = 64 − 20 × (height ÷ waist); women: RFM = 76 − 20 × (height ÷ waist)
Worked example
Example: Relative fat mass (estimated body fat) = 34.9%
- Inputs: Sex: Female; Units: inches; Height: 72; Waist (at the navel): 35.
- Formula: Men: RFM = 64 − 20 × (height ÷ waist); women: RFM = 76 − 20 × (height ÷ waist)
- Result: Relative fat mass (estimated body fat) = 34.9%
Questions people ask
Where do I measure my waist?
Around the navel, standing, after breathing out normally.
Is it better than BMI?
It tracks body fat more closely, but neither is a diagnosis.