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Body roundness index (BRI) calculator

Short answer

Body roundness index uses your waist and height to model your body as an ellipse: BRI = 364.2 − 365.5 × √(1 − (waist ÷ 2π)² ÷ (0.5 × height)²). A 90 cm waist at 175 cm gives a BRI of 3.6. In 32,995 US adults, compared with a BRI of 4.5–5.5, risk of death from any cause was 25% higher below 3.4 and 49% higher at 6.9 or more. That is an average across people, not a personal prediction.

Last reviewed 27 October 20262 published sourcesNot medical advice

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Body roundness index calculator

Uses your waist and height, the two measurements behind the body roundness index (BRI).

Units
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Enter your waist and height.

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Body roundness index by waist and height
Waist160 cm tall170 cm tall180 cm tall
70 cm2.31.91.5
80 cm3.42.82.4
90 cm4.63.93.4
100 cm6.05.24.5
110 cm7.66.55.7
BRI = 364.2 − 365.5 × √(1 − (waist ÷ 2π)² ÷ (0.5 × height)²).
All-cause mortality by BRI group (Zhang et al., 2024)
BRIRisk vs the 4.5–5.5 group
Under 3.425% higher (hazard ratio 1.25)
3.4 to under 4.5Between the two: the curve is U-shaped
4.5 to 5.5Reference group
Over 5.5 to under 6.9Between the two: the curve is U-shaped
6.9 or more49% higher (hazard ratio 1.49)
After full adjustment. The study reports figures for the lowest and highest groups against the reference.

Where BRI comes from

Thomas et al. modelled the body as an ellipse from waist circumference and height. Their body roundness index slightly improved predictions of body fat and visceral fat, measured by DXA and MRI, compared with BMI, waist or hip circumference (Thomas et al., 2013 (BRI)).

Zhang et al. followed 32,995 US adults from national surveys for a median of about 10 years. Mean BRI rose over 1999–2018, and mortality followed a U shape: against the middle group (4.5–5.5), the hazard was 25% higher below 3.4 and 49% higher at 6.9 or more (Zhang et al., 2024). Compare with your waist-to-height ratio or BMI.

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Common questions

What is a normal body roundness index?

There is no official cut-off. In a 2024 study of US adults, average BRI rose from 4.80 to 5.62 between 1999 and 2018, and the middle group, with a BRI of 4.5–5.5, was the reference that the higher and lower groups were compared with.

Is BRI better than BMI?

In the study that introduced it, BRI slightly improved predictions of body fat and visceral fat compared with BMI or waist alone, because it combines waist and height. It is newer, with less research behind it than BMI or waist-to-height ratio.

Does a high BRI mean I am unhealthy?

No. The study found higher average risk in groups of people, after accounting for other factors; it does not predict any one person's health. Read it alongside other measures and talk to a clinician about any concerns.

Sources

Figures on this page were checked against these publications on 27 October 2026.

  1. Thomas DM, Bredlau C, Bosy-Westphal A, Mueller M, Shen W, Gallagher D, Maeda Y, McDougall A, Peterson CM, Ravussin E, Heymsfield SB. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity. 2013;21(11):2264–2271. doi.org/10.1002/oby.20408
  2. Zhang X, Ma N, Lin Q, Chen K, Zheng F, Wu J, Dong X, Niu W. Body roundness index and all-cause mortality among US adults. JAMA Network Open. 2024;7(6):e2415051. doi.org/10.1001/jamanetworkopen.2024.15051

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