Body roundness index (BRI) calculator
BRI models the body as an ellipse, so the wider your waist relative to your height, the higher the number.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter waist and height.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
BRI = 364.2 − 365.5 × √(1 − (waist ÷ 2π)² ÷ (0.5 × height)²), with waist and height in meters (Thomas et al. 2013).
Example
Inputs: Waist = 85 cm, Height = 175 cm. Result: Body roundness index: 3.09; Waist-to-height ratio: 0.49.
Limits and caveats
- There are no official cut-offs yet, so the tool shows the number without a category.
- Studies link higher values to higher risk, but the index does not diagnose anything.
Questions about this tool
What is a normal BRI?
Most adults fall roughly between 1 and 10; higher values mean a rounder shape and more belly fat.
Why is BRI getting attention now?
Large studies since 2024 linked higher BRI with higher mortality, so it is being used alongside BMI.
How is it different from waist-to-height ratio?
Both use waist and height, but BRI turns them into a measure based on an elliptical body shape.