BRI Calculator
A person who is 175 cm tall with a 100 cm waist has a BRI of 4.80, which lands in the higher adult roundness band used by this tool. This BRI calculator estimates body roundness index from waist circumference and height using the established Thomas body roundness model. Enter both measurements in the same unit to get the score, a waist-to-height ratio, and a cautious adult screening note.
Quick answer
BRI uses waist circumference and height rather than body weight.
Use the same unit for both measurements. This tool gives a cautious adult screening estimate only and does not convert between inches and centimeters.
What this tells you
- •BRI uses waist circumference and height rather than body weight.
- •This tool works with centimeters or inches as long as both inputs use the same unit.
- •The screening bands used here are broad adult reference bands, not universal clinical cutoffs.
- •The result is a screening estimate, not a diagnosis or a direct body fat measurement.
How to Use
- 1Choose centimeters or inches.
- 2Enter your waist circumference.
- 3Enter your height in the same unit.
- 4Calculate to see your BRI score, waist-to-height ratio, and the cautious adult screening note used here.
How It Works
Formula
BRI = 364.2 - 365.5 × √(1 - ((waist / (2π))² / (0.5 × height)²))
Equivalent same-unit form: BRI = 364.2 - 365.5 × √(1 - (waist ÷ height ÷ π)²)
Waist-to-height ratio = waist ÷ heightThe Thomas body roundness model treats the body as a waist-and-height shape estimate. Because waist and height use the same unit, the ratio stays the same whether you enter centimeters or inches. The score is then compared with the broad adult screening bands used by this tool. Those bands are a cautious reference, not a universal diagnostic standard.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Higher adult roundness example
The formula uses a waist-to-height ratio of 100 ÷ 175 = 0.5714. That produces a BRI of 4.80 after rounding, which falls in the higher adult roundness band used here.
Broad adult midrange example
Because both measurements use inches, no unit conversion is needed. A 36 ÷ 70 waist-to-height ratio equals 0.5143, which gives a BRI of 4.04 after rounding.
Broad Adult Screening Bands Used Here
These bands are included for cautious adult screening context only.
| BRI band | Label shown here | How to read it |
|---|---|---|
| Below 3.41 | Lower adult roundness score | Below the broad adult midrange used by this tool |
| 3.41 to 4.44 | Broad adult midrange | Inside the broad adult midrange used by this tool |
| 4.45 to 6.91 | Higher adult roundness score | Above the broad adult midrange used by this tool |
| Above 6.91 | Much higher adult roundness score | Well above the broad adult midrange used by this tool |
These adult screening bands are not universal clinical standards. Research, calculators, and populations vary, so BRI should be interpreted cautiously and alongside other health information.
Common mistakes
- Mixing inches for waist with centimeters for height
- Measuring the waist at different body landmarks from one check to the next
- Treating BRI as a diagnosis or as a direct reading of visceral fat
Limitations
This calculator uses waist and height only. It does not include weight, age, sex, ethnicity, pregnancy, muscle mass, edema, or medical history. BRI is still an emerging anthropometric measure compared with BMI, and the broad adult screening bands used here are not universal clinical cutoffs. This tool is not intended for children.