Calculate Body Roundness Index from waist and height to estimate central adiposity and cardiometabolic risk.
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Units
3.41
BRI score
0.503
Waist-height ratio
88
Waist (cm)
| Category | BRI range |
|---|---|
| Very slim | < 3.41 |
| Normal | 3.41–6.9 |
| Moderately round | 6.9–10.0 |
| Very round | ≥ 10.0 |
Also in Body Metrics
Body Composition
This calculator computes Body Roundness Index (BRI), which models the body as an ellipse using waist circumference and height to quantify central body shape and estimate cardiometabolic risk.
Body Roundness Index was developed by Thomas et al. (2013) as a geometric measure of body shape. It models the body's cross-section as an ellipse and uses waist circumference and height to calculate how 'round' the body is — hence the name. Higher values indicate greater central adiposity.
BRI values range from close to 1 (very slim) to about 20 (highly round body shape). The formula is: BRI = 364.2 − 365.5 × √(1 − (WC/2π)² / (height/2)²), where all measurements are in metres.
BMI does not distinguish between central and peripheral fat distribution. A person with a normal BMI but high waist circumference — so-called metabolically obese normal weight — may carry significant cardiometabolic risk that BMI misses. BRI, which directly uses waist circumference, captures this distribution.
Studies have found BRI to be a strong predictor of visceral adiposity, insulin resistance, dyslipidaemia, and cardiovascular risk — often outperforming BMI and waist circumference alone. BRI integrates body shape information from both the waist and height simultaneously.
Measure at the natural waist — midway between the lowest rib margin and the iliac crest (the hip bone). Stand upright, breathe out normally, and measure without pulling the tape tight. Avoid measuring over clothing.
Waist circumference is sensitive to measurement technique. Consistent measuring conditions (same time of day, same measurement point) are important if you are tracking changes over time.
Frequently asked questions
BRI and BMI measure different things. BMI reflects total body mass relative to height; BRI reflects the shape of the body cross-section at the waist. BRI may be more sensitive to central adiposity and metabolic risk in some populations, but BMI has far more validation data. Using both together provides a more complete picture.
A BRI between 3.41 and 6.9 is classified as normal in this calculator. Values below 3.41 are very slim and values above 6.9 indicate elevated central adiposity. As a relatively new metric, population-level norms are still being established.
BRI is closely related to waist-to-height ratio (WHtR). Both use the same two measurements. BRI uses a more complex geometric formula that produces a continuous index, while WHtR is a simple ratio. Research suggests both are similarly predictive of cardiometabolic risk.
Related
These related calculators come from the same leaf category, nearby sibling categories, or the same top-level topic.
Estimate Body Adiposity Index from hip circumference and height using the Bergman formula, with sex-specific underfat-to-obese categories.
Check body mass index with metric or imperial units, then compare the result with standard adult BMI ranges and a height-based healthy weight estimate.
Calculate waist-to-height ratio and compare your waist measurement with common adult screening thresholds.
Estimate Relative Fat Mass from height and waist circumference using the Woolcott–Bergman formula, with sex-specific body fat categories.
