What is Relative Fat Mass (RFM)?
Relative Fat Mass (RFM) is a simple formula developed by researchers at Cedars-Sinai Medical Center in 2018. It was designed to address the major flaws of the Body Mass Index (BMI). While BMI only considers weight and height, often misclassifying muscular individuals as overweight, RFM uses waist circumference to better estimate body fat percentage and detect abdominal obesity.
RFM vs. BMI vs. Navy Method
| Method | Inputs | Pros & Cons |
|---|---|---|
| BMI | Weight, Height | Least accurate. Misclassifies muscle as fat. |
| Unique (RFM) | Height, Waist | More accurate than BMI. Simple to measure. |
| Navy Method | Height, Waist, Neck, Hips | Most accurate tape method, but complex. |
How to Measure
- Use a flexible tape measure.
- Waist: Place the tape measure at the top of your hip bone (iliac crest), usually crossing your belly button.
- Height: Stand straight against a wall without shoes.
Why it matters
Abdominal fat is a better predictor of health risks (like diabetes and heart disease) than total weight.
Check full Body Fat CalculatorFrequently Asked Questions
Why don't I need to weigh myself?
RFM is based on geometry (Height vs. Waist size). It assumes weight is irrelevant if we know your proportions. A high waist-to-height ratio typically indicates higher body fat.
Is this accurate for athletes?
Yes, generally better than BMI. Athletes often have small waists relative to their height, even if they are heavy due to muscle. RFM correctly identifies them as "Lean", whereas BMI might classify them as "Overweight".
Tools & Data Verified by the EverydayCalculators Medical Research Team.
Last updated: January 2026.