Body measurements Health Calculators

Relative Fat Mass (RFM)

RFM Calculator (Relative Fat Mass)

This RFM calculator (or Relative Fat Mass calculator) predicts body fat mass using only two body measurements – height and waist circumference. This estimation is more accurate than the well-known body mass index (BMI), which often misclassifies obesity.

RFM has been generally validated and a recent 2020 study by the original authors has also established gender specific cut-off points for obesity.

The relative fat mass equation is gender specific:

  • RFM for adult males = 64 – 20 x (Height / Waist circumference)
  • RFM for adult females = 76 – 20 x (Height / Waist circumference)

For the best results, when using a tape measure and recording the height and waist circumference, the tape measure should be placed at the top of the hip bone and wrapped around the body. You can use either the Metric or the English system, whichever is more convenient, but ensure that both measurements are input in the same unit system.

Woolcott and Bergman (2020) propose RFM cut-offs of 40% for females and 30% for males to diagnose obesity and higher mortality risk.

The relative fat mass result can also be interpreted in line with the cut-offs established by the American Council on Exercise:

Classification Females (% fat) Males (% fat)
Essential fat 10-13% 2-5%
Athletes 14-20% 6-13%
Fitness 21-24% 14-17%
Average 25-31% 18-24%
Obese 32% and higher 25% and higher

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