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Body Roundness Index (BRI)

The Body Roundness Index (BRI) is a measure of body shape and fat distribution, designed as an improvement to the Body Mass Index (BMI). It estimates the level of abdominal obesity and overall health risk based on Height and Waist circumference measurements.

Background

The BRI is designed as an improvement to BMI, as it attempts to get a measure of someone's shape. The BRI value is based on eccentricity, the degree of circularity of an ellipse. Such values range between 0 and 1, with 0 characterizing a perfect circle, and 1, a vertical line. The BRI formula converts the eccentricity value to a workable range between 1 and 16. A wider abdominal area (increased "roundness") would indicate greater abdominal fat, with belly fat mass associated with a higher risk of negative health conditions.

BRI Formula

The following formula is used to calculate BRI (though it is much easier to put your values in the calculator below).

BRI = 364.2 − 365.5 × √(1 − [waist circumference / 2π]2 / [0.5 × height]2)

BRI Calculator

The units for height and weight can be either cm or inches (or any other measure as long as they are the same units).

Height:

Waist Circumference:

Interpretation

A higher BRI value indicates a rounder body shape, and therefore a higher risk of obesity-related health conditions. BRI scores usually range from 1 to 16, with most people falling between 1 and 10. Here are BRI values and the associated risk level.

< 3.41 — Low Risk
3.41 to 4.44 — No Statistically Significant Risk
4.45 to 6.91 — Moderate Risk
> 6.91 — High Risk

Should I Use It?

Body Roundness Index (BRI), as an alternative to the traditional Body Mass Index (BMI), offers a more nuanced approach to assessing body composition. Unlike BMI, which only considers height and weight, BRI attempts to account for fat distribution. However, while BMI is quick and easy to calculate, BRI relies on a more intricate algorithm, which may limit its accessibility for everyday use. Additionally, while BRI offers improved accuracy, it is still not a perfect measure of health risk level, and it should still be used alongside other health indicators, like blood pressure, cholesterol and blood sugar levels.

References

Thomas DM, Bredlau C, Bosy-Westphal A, et al. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity (Silver Spring). 2013;21(11):2264-2271.
Zhang X, Ma N, Lin Q, Chen K, Zheng F, Wu J, Dong X, Niu W. Body Roundness Index and All-Cause Mortality Among US Adults. JAMA Netw Open. 2024 Jun 3;7(6):e2415051.

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About the measures of Height and Waist girth
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Skinfold measurement — calipers are used to measure the thickness of the skin at a range of sites around the body.