MasterTool

Body Roundness Index Calculator

Calculate your Body Roundness Index (BRI) from height and waist circumference using the Thomas et al. (2013) formula.

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What this tool does

Calculate your Body Roundness Index (BRI) from height and waist circumference using the Thomas et al. (2013) formula. BRI models the body as an ellipse from waist and height. It is a research index gaining attention as a BMI alternative; there are no official clinical BRI categories.

How to use the Body Roundness Index Calculator

  1. Enter or select waist circumference in in.
  2. Enter or select height in in.
  3. Read the calculated result; change any measurement to compare alternatives.

Formula

BRI = 364.2 − 365.5 × √(1 − ((waist/2π)² / (0.5 × height)²)) (Thomas et al. 2013)
waist
Waist circumference (in, before metric conversion)
height
Height (in, before metric conversion)

BRI models the body as an ellipse from waist and height. It is a research index gaining attention as a BMI alternative; there are no official clinical BRI categories.

Worked example

For body roundness index calculator, the following measurements illustrate the exact method: Waist circumference: 34; Height: 69.

Inputs

  • Waist circumference34 in
  • Height69 in

Result

  • Body Roundness Index (BRI)3.22

Results explained

Body Roundness Index (BRI)
Body Roundness Index (BRI) from the formula above. BRI models the body as an ellipse from waist and height. It is a research index gaining attention as a BMI alternative; there are no official clinical BRI categories.

Frequently asked questions

BRI (Thomas et al., 2013) estimates body shape — and indirectly visceral fat — from height and waist circumference by modelling the torso as an ellipse. Values typically run from about 1 (very lean/round-free) upward.

BMI uses weight, which cannot locate fat. BRI uses waist circumference, so it reflects central adiposity — the reason it has drawn research attention as a complement or alternative to BMI since 2024.

There are no official clinical BRI categories. Published cohort work associates higher BRI (roughly above 5–6) with higher cardiometabolic risk, but treat any cut-off as research context, not a target.

Midpoint between the lowest rib and the iliac crest, relaxed, end of a normal breath, tape snug on bare skin or light clothing.

No. BRI is an estimate from two tape measurements; imaging is required to measure visceral fat directly.