Relative Fat Mass (RFM) Calculator
Estimated body fat percentage from height and waist circumference, by the RFM equation, with the fat and fat-free mass for your weight.
Results
What this tool does
Relative fat mass was published by Orison Woolcott and Richard Bergman in Scientific Reports in 2018, fitted to DXA body scans of thousands of American adults from the NHANES survey. It needs only a tape measure and a height, and in that study it estimated body fat better than BMI, especially in telling apart people of similar weight with different shapes. Measure the waist at the navel, standing, after breathing out normally. Like any formula built on one population, it can be off by several points for an individual, and it is not designed for children, pregnant women or very muscular athletes.
Formula
RFM = 64 − 20 × (height ÷ waist) + 12 × (1 for women, 0 for men)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
ht | Height | cm |
wc | Waist circumference (at the navel) | cm |
sx | Sex | — |
w | Weight | kg |
RF | Relative fat mass (estimated body fat) | % |
FM | Fat mass | kg |
LM | Fat-free mass | kg |
HW | Height-to-waist ratio | — |
Worked example
- Height170 cm
- Waist circumference (at the navel)85 cm
- Sex0
- Weight70 kg
- Relative fat mass (estimated body fat)24.0 %
- Fat mass16.8 kg
- Fat-free mass53.2 kg
- Height-to-waist ratio2.00
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.