What BRI measures
Body Roundness Index (BRI) describes how round or slim your body is, using waist circumference and height in an ellipse-based formula. Unlike BMI, it focuses on central (abdominal) fat, which research links more closely to metabolic risk. Values typically range from about 1 to 16, with higher meaning a rounder shape. For an estimate of total fat percentage rather than shape, use the body fat calculator.
How to use this calculator
Enter your waist circumference and height in centimetres. The result is your BRI. Measure your waist at the navel, standing relaxed, with the tape snug but not compressing the skin. A height-based reference weight comes from the ideal weight calculator.
BRI vs. BMI
BMI uses only weight and height, so a muscular person can score high without excess fat. BRI adds waist size, capturing where fat sits. Many researchers consider waist-based measures better predictors of cardiovascular and metabolic risk. Compare with the BMI calculator and waist-to-hip ratio.
Use it as one signal
No single number captures health. BRI is a useful screen for body shape, but trends, fitness, blood markers and a clinician's view matter more. This tool is for general information only, not medical advice.
Frequently asked questions
- How is BRI calculated?
- BRI uses waist circumference and height in an ellipse eccentricity formula: 364.2 − 365.5 × √(1 − ((waist ÷ 2π) ÷ (0.5 × height))²).
- What is a good BRI?
- There's no universal cutoff, but lower values indicate a slimmer profile and less central fat. Track your own trend and discuss specifics with a clinician.
- Is BRI better than BMI?
- BRI includes waist size, so it reflects central fat that BMI misses. Many find it a better risk signal, though both are screening tools, not diagnoses.
- Where do I measure my waist?
- At the navel, standing relaxed after a normal breath out, with the tape snug but not digging in.
- Does BRI need my weight?
- No. BRI is worked out from waist circumference and height only, so a tape measure is all you need. That is also why two people at the same weight can have very different BRI values.