Body Roundness Index Calculator

What the Body Roundness Index is

The Body Roundness Index, or BRI, was introduced in 2013 by researchers who modelled the body as an ellipse. It combines your waist circumference with your height to estimate how round your body is, which tracks the amount of fat stored around your organs.

That matters because two people with the same BMI can carry very different risk. A muscular person and a person with a large waist can share a BMI of 28. Their BRI will not match.

Why it is getting attention now

In 2024 a study in JAMA Network Open followed nearly 33,000 US adults from the NHANES survey for up to two decades. People in the highest BRI band had roughly 50% higher all-cause mortality than those in the middle band. People in the lowest band also had higher risk, which is why very low scores are flagged too.

That study, and wider frustration with BMI, is why you will see BRI described as the measurement that could replace BMI. In practice clinicians use it alongside BMI rather than instead of it.

The waist-to-height ratio rule

The calculator also gives your waist-to-height ratio, a simpler measure with strong research behind it. The rule of thumb is to keep your waist under half your height, a ratio below 0.50.

A ratio above 0.50 is linked with higher risk of type 2 diabetes, high blood pressure and heart disease, even when BMI looks normal.

How to measure your waist properly

Stand up straight and breathe out normally. Wrap a soft tape around your bare stomach at the level of your navel, keeping it level all the way round. It should sit snug without pressing into the skin. Measure twice and use the average.