Body Roundness Index Calculator
BRI from height and waist circumference — Thomas eccentricity-style index. Click any i for detail.
Height & waist
Height (cm)
i
Height
Standing height. |
|
|---|---|
Waist (cm)
i
Waist
Waist circumference. |
How to use this calculator
- Enter height in cm.
- Enter waist in cm.
- Read BRI.
- Use as an anthropometric index, not a diagnosis.
Results explained
Body Roundness Index models the body as an ellipse using height and waist. The Thomas et al. formula is BRI = 364.2 − 365.5 × √(1 − (wc/(2π))² / (0.5×height)²) with meters. Higher BRI suggests greater roundness.
Quick reference: BRI
BRI = 364.2 − 365.5 × √(1 − eccent²) with waist/height geometry.
| Item | Detail |
|---|---|
| Inputs | Height & waist in cm (converted to m) |
| Typical adult range | Often roughly ~1–10+ |
| Vs BMI | Uses waist, not weight |
| Clamp | Radical argument limited to [0,1] |
Educational index only — not medical advice.
How the estimate is built
BRI = 364.2 − 365.5 × sqrt(1 − ((WC/(2π))^2 / ((0.5 H)^2))).
Example scenario
175 cm, waist 85 cm → BRI ≈ 3.3.
FAQ
Inches?
Convert to cm first.
Where to measure waist?
Use a consistent protocol (often iliac crest or navel).
Healthy BRI cutoffs?
Research cut-points vary by study — not hard-coded here.
Need hip too?
Not for BRI — see WHR for waist/hip.