BRI Formula
The BRI formula calculates the roundness of your body shape using your waist and height. It's a little more complicated than BMI, but our calculator does all the work for you.
BRI Formula
First we calculate the waist-to-height ratio by dividing your waist circumference by your height.
WHtR = Waist Circumference / Height
Then we calculate the "eccentricity" (how non-circular the shape is):
Eccentricity = √(1 - (WHtR / π)²)
Lastly we use the eccentricity variable to calculate your BRI:
BRI = 364.2 - (365.5 × Eccentricity)
Example
- Height: 175 cm (1.75 m)
- Waist: 85 cm (0.85 m)
WHtR = 0.85 / 1.75 = 0.486Eccentricity = √(1 - (0.486 / 3.14159)²) = √(1 - 0.0239) = 0.988BRI = 364.2 - (365.5 × 0.988) = 364.2 - 361.1 = 3.1
The value of 3.1 is classified as very lean in the table below.
BRI Classification
| BRI Value | Classification | Health Risk |
|---|---|---|
| < 3.41 | Very Lean | Very Low |
| 3.41 - 4.45 | Lean | Low |
| 4.45 - 5.46 | Average | Average |
| 5.46 - 6.91 | Above Average | Increased |
| > 6.91 | High Roundness | High |
History
BRI was developed by Diana Thomas et al in 2013. Essentially it models the shape of your body as an oval, and the formula calculates how round that oval is.
A rounder shape (higher BRI) means more belly fat, while a more oval shape (lower BRI) means less belly fat.