Body Roundness Index calculator
A measure of how round your body is, from your waist and height. Diana M. Thomas and colleagues at the Center for Quantitative Obesity Research, Montclair State University, published it in 2013. They modelled the body as an ellipse and tested how well the index predicted body fat and the fat around the organs, both measured by scans. It reads the same two numbers as the waist to height ratio, through a different equation.
What it is doing
The index models your body as an ellipse whose height is your height and whose width comes from your waist, then reports how far that ellipse is from a circle. A very round shape scores high, a narrow one scores low.
Because it is built from waist and height, it carries the same information as thewaist to height ratio and expresses it differently. If you only want one of the two, take the ratio: it is easier to read and it is the measure current guidance actually recommends.
Why there are no bands on this page
Every other calculator here reads your number against published cut points. This one does not, because no health body has adopted any. Putting a green band on it would be inventing a threshold, which is exactly the thing this site exists not to do.
Common questions
What is the Body Roundness Index?
A measure introduced by Thomas and colleagues in 2013 that treats the body as an ellipse and works out how round that ellipse is, from your waist and your height. It typically runs from about 1 to about 16, where a higher number means a rounder shape.
Is BRI better than BMI?
It is better at one specific thing: estimating fat around the organs, because it uses a waist measurement and BMI does not. It is not a replacement for BMI, and it is considerably less established. BMI has decades of outcome data behind its cut points; BRI does not.
What is a good BRI?
There is no officially adopted threshold, which is the honest answer. Studies have proposed various cut points and they do not agree with each other. Treat your own number as a baseline and watch whether it moves, rather than comparing it with a threshold somebody published once.
Should I use this or waist to height?
Waist to height, for most purposes. It uses the same two measurements, it is far easier to interpret, and it is the one current NICE guidance points at. BRI is here because the app calculates it and because some people specifically want it.
Sources
Every figure above comes from one of these. Check them.
Free, no account, and it works offline. 100,000+ downloads on Google Play.
This is not medical advice. Body Numbers is a calculator. It does not diagnose, treat or monitor any condition, and no number it produces should replace a conversation with a doctor or a dietitian. If a result worries you, or if you are pregnant, unwell, or under eighteen, speak to a health professional.
