Body Roundness Index
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Body Roundness Index (BRI) Calculator

A newer alternative to BMI using waist circumference and height

Body Roundness Index (BRI) is a newer body-shape metric that models your body as an ellipse, using your waist circumference and height. It was designed to better reflect body fat distribution than BMI, which only uses height and weight. BRI is newer research and doesn't yet have official clinical cutoffs the way BMI does — treat the ranges below as general reference points, not a diagnosis.

Your measurements

Measure your waist at the narrowest point, usually just above the belly button.

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body roundness index
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General reference points

Compare against your BMI and Waist-to-Hip Ratio for a fuller picture.
BRI research is still evolving, and these reference points are general approximations, not official diagnostic cutoffs. This is not a substitute for professional body composition assessment.

How it works

  1. Enter your height and waist circumference.
  2. We model your body as an ellipse using the formula BRI = 364.2 − 365.5 × √(1 − (waist/2π)² / (0.5×height)²).
  3. The result estimates your body roundness, a shape-based measure researchers have found correlates with visceral fat and body fat percentage.

This metric is newer than BMI and still an active area of research. Use it as one additional data point, not a standalone diagnosis.

Frequently asked questions

A newer body-shape metric, proposed in 2013 and gaining renewed research attention, that models your body as an ellipse using waist circumference and height. It's designed to better reflect body fat distribution than BMI.
BMI uses only height and weight, treating everyone's shape the same. BRI uses waist circumference and height to estimate body shape more directly, correlating better with visceral fat and body fat percentage than BMI does.
Not yet in the same standardized way. BRI is newer than BMI, and most research uses population quintiles rather than fixed clinical cutoffs. The reference ranges shown here are general approximations, not official diagnostic thresholds.
BRI = 364.2 − 365.5 × √(1 − (waist circumference / (2π))² / (0.5 × height)²), based on modeling the body as an ellipse. Introduced by Thomas et al. in a 2013 study.

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