Relative Fat Mass (RFM) Calculator
Enter your height and waist in the same unit to estimate your body fat percentage with the RFM formula.
- Nothing you type is stored
- Free
- No signup
Estimated body fat (RFM)
24.5%
Below the obesity cut-off- Obesity cut-off for you
- 30%
An estimate for general information, not medical advice.
How to use
- Choose male or female and the unit.
- Enter your height.
- Measure your waist at the navel and enter it.
Good to know
RFM = 64 − 20 × (height ÷ waist) + 12 × sex, where sex is 0 for men and 1 for women (Woolcott and Bergman, Scientific Reports 2018). Height and waist must be in the same unit.
In the original study, RFM matched DEXA body fat better than BMI did, and body-fat-defined obesity was RFM of 30% or more in men and 40% or more in women. The study used US adults; Indians may carry more fat at the same waist size.
It is an estimate, best for tracking change. Measure the waist the same way each time. Not for children or pregnancy.
Questions
What is a normal RFM?
Below about 30% for men and 40% for women by the study's obesity cut-offs. Lower is not always better: very low fat is also unhealthy.
How is RFM different from BMI?
BMI uses weight, which includes muscle. RFM uses waist size, which tracks body fat more closely.
Do I need to weigh myself?
No. Only height and a tape measurement around the waist.
Is RFM accurate for Indians?
It was developed on US data, so treat it as a rough guide. Pair it with the Asian waist cut-offs of 90 cm (men) and 80 cm (women).
Is my data stored?
No. Everything is calculated on your device.