The Body Roundness Index (BRI) is based on an ellipse with the major axis a person's height and the minor axis the waist. As a person becomes more obese the person appears to be more round. The authors are from Montclair State University (New Jersey), Christian-Albrechts University, St. Luke's-Roosevelt Hospital and Pennington Biomedical Research Center in Baton Rouge.


(1) height in centimeters

(2) waist circumference in centimeters


body roundness index =

= 364.2 - (365.5 * (eccentricity))


eccentricity =

= c/a


c = SQRT((a^2) - (b^2))


a = (height)/2


b = (waist) / (2 * PI()) = radius of a circle around the waist


When this is multiplied out


eccentricity =

= SQRT(1 - (((waist)^2) / (((height)^2) * ((PI())^2))))



A thin, lean person will have an BRI of around 1.

The maximum BRI is around 16 and indicates a very round individual.

There is a range for BRI which is ideal for a given patient.

The higher the BRI the higher the percent body fat.

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