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Body Roundness Index Calculator

Find your Body Roundness Index from your waist circumference and height, and see your body-shape category.

Result

4.20
Normal

How it is calculated

The tool models the body as an ellipse. Waist and height are entered in centimetres and converted to metres. It then computes r = (waist / 2π)² / (0.5 × height)², the eccentricity e = √(1 − r), and finally BRI = 364.2 − 365.5 × e. A rounder midsection gives a lower eccentricity and therefore a higher BRI. The category rule in this tool is: below 3.41 is Low, 3.41 to 6.9 is Normal, and above 6.9 is High. If the waist is so large relative to height that r reaches 1 (waist of about π times height), no result is shown. Weight, age and sex are not used, and the category cut-offs are the tool's own simple bands rather than a diagnosis.

Worked example

A person is 175 cm tall with a 95 cm waist. In metres that is 1.75 and 0.95. The waist radius term is 0.95 / (2π) = 0.1512, and half the height is 0.875. Squaring and dividing gives r = 0.0229 / 0.7656 = 0.0299. Eccentricity: √(1 − 0.0299) = 0.9850. BRI = 364.2 − 365.5 × 0.9850 = 4.20, which falls in the Normal band (3.41 to 6.9). With the same height and a 110 cm waist the BRI would rise to 6.09.

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Common mistakes

  • Entering inches or metres. Both fields are in centimetres, so a 1.75 height or a waist of 37 inches gives a meaningless result.
  • Measuring the waist over clothing or at the hips. It should be taken around the natural waist, level with the navel, otherwise the index is shifted.
  • Comparing the number with a BMI scale. BRI uses its own scale, and values around 3 to 7 are typical of this tool's bands, not BMI-like numbers.
  • Reading the category as a medical verdict. It is only a rough band on a body-shape index; weight, muscle and age are not considered.
  • Using it for children or during pregnancy. The tool applies the same adult-style formula and bands to everyone, so the category is not meaningful in those cases.

Sources

About this calculator

This calculator finds your Body Roundness Index (BRI), a body-shape measure developed as an alternative to BMI that models the body's cross-section as an ellipse using waist circumference and height, producing a score that correlates with visceral fat and cardiometabolic risk better than BMI does for some populations. Enter your waist and height to see your BRI and whether it falls in the low, normal, or high range.

Researchers and health-conscious individuals use it alongside BMI and waist-to-height ratio for a fuller picture of body shape, since BRI doesn't require weight and captures central fat distribution that BMI alone misses. It's a screening estimate, not a diagnostic tool.

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Comments (1)

  • Editorial team

    One way to read the score: BRI depends only on the ratio of waist to height, not on either figure alone. Anyone whose waist is exactly half their height gets 3.36 here, which falls in the tool's Low band, whether they are 160 cm or 190 cm tall. So the useful habit is to measure the waist the same way each time and watch the trend. Do you track waist measurements over weeks or months?

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