Estimate Body Roundness Index (BRI) from height and waist circumference. Compare metric and US measurements and see how measurement changes affect the result.
Your measurements
Measure the waist consistently with a level tape that is snug but does not compress the skin.
Your results
Body Roundness Index
Geometric body-shape estimate
| Waist-to-height ratio | 0.471 |
|---|---|
| Ellipse eccentricity | 0.989 |
| Waist 1 cm smaller | 2.75 |
| Waist 1 cm larger | 2.96 |
BRI is a screening estimate—not a direct measurement of fat, visceral fat, fitness, or disease risk.
How Body Roundness Index works
BRI models the body as an ellipse using height and waist circumference. The equation is 364.2 − 365.5 × √(1 − [waist ÷ (π × height)]²). Height and waist may be entered in any matching length unit.
The index was introduced as a way to describe body shape and examine relationships with body-fat and visceral-fat measurements in populations. It does not require body weight, but accurate waist placement remains important.
For a more consistent result
- Stand upright with your abdomen relaxed.
- Keep the measuring tape horizontal.
- Measure at the same anatomical location each time.
- Track changes over time instead of relying on one reading.
Frequently asked questions
Is BRI better than BMI?
They use different inputs. BMI uses height and weight; BRI uses height and waist circumference. Neither provides a complete individual health assessment.
What is a good BRI?
There is no single universal cutoff appropriate for every age, population, or clinical purpose. Discuss personal interpretation with a qualified professional.
Does BRI measure visceral fat directly?
No. It is a geometric estimate associated with body shape, not an imaging or laboratory measurement.
Can children use this calculator?
This page is intended for general adult education. Children require age-appropriate growth and health assessment.
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Health disclaimer: This calculator provides an educational estimate and does not diagnose any condition. Seek professional advice for personal health decisions.