Relative Fat Mass (RFM) Calculator - Estimate Body Fat from Height and Waist
Relative Fat Mass Calculator
Body fat from height and waist, no scale needed
Two Measurements
RFM only needs your height and the circumference of your waist, so a tape measure is enough.
Beyond BMI
BMI cannot tell muscle from fat. RFM was designed to estimate body fat directly and, in its validation study, agreed with scans better than BMI did.
Standard Ranges
The result is placed in the widely used ranges for essential fat, athletes, fitness, average and obese.
Private
Nothing you enter is stored or sent.
How Relative Fat Mass Works
Relative Fat Mass was published in 2018 by Orison Woolcott and Richard Bergman. The formula is 64 minus 20 times height divided by waist for men, and 76 minus the same term for women. The idea is simple: for a given height, a larger waist means more fat around the middle, so the ratio of height to waist predicts body fat percentage.
It is an estimate. Waist-based formulas can be wrong for people with unusual builds, for children and teenagers, during pregnancy and for some ethnic groups, and they say nothing about where fat is stored deeper in the body. Measure at the level of the navel after breathing out normally, and measure the same way each time to track change. Use the result alongside other measurements and a health professional’s advice.
Key Takeaways
- Adults only: The formula was developed for adults and is not meant for children, teenagers or pregnant women.
- Measure carefully: A 2 cm error in waist changes the result by about a percentage point.
- Related calculators: See also the Body Fat Calculator, the Waist-to-Height Ratio Calculator and the BMI Calculator.