How this calculator works
An ellipse with semi-major axis height/2 and semi-minor axis waist/(2pi) has a calculable eccentricity. Thomas and colleagues mapped that eccentricity to BRI. BRI is an index, not measured visceral fat or a universal health category. Both lengths are converted to metres so their ratio is unitless. The result is an estimate for information only and is not medical advice.
Formula
e = sqrt(1 - [waist/(pi x height)]²). BRI = 364.2 - 365.5e.
Worked example
At 170 cm tall with an 80 cm waist, eccentricity is about 0.98872 and BRI is about 2.82. At 180 cm with a 90 cm waist, BRI is about 3.36.
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Frequently asked questions
Does BRI measure visceral fat?
No. The original study explored associations with measured fat; this calculation returns only the geometric index.
Which waist site should I use?
Use a consistent, level circumference measurement and record its site. Different waist protocols can give different results.
Is there a healthy BRI cutoff?
This page does not assign one. Clinical interpretation depends on population evidence and the rest of a health assessment.