BRI Calculator
Estimate Body Roundness Index from waist circumference and height, then interpret where your result sits on practical roundness ranges.
Body Roundness Index
Leaner waist-to-height profile for most adults.
BRI Interpretation Ranges
These are practical body-roundness ranges based on BRI. Use them as trend categories, not a diagnosis.
| BRI RANGE | CATEGORY |
|---|---|
| 0.00-3.41 | Very Lean Lower roundness profile relative to height and waist. |
| 3.41-4.45 | Lean Leaner waist-to-height profile for most adults. |
| 4.45-5.46 | Average Mid-range body roundness; best interpreted with trend data. |
| 5.46-6.91 | Above Average Higher waist-centered roundness compared with average ranges. |
| 6.91+ | High Roundness High roundness profile; use with clinical context and long-term trends. |
What This BRI Calculator Shows
BRI (Body Roundness Index) estimates central body roundness from your waist and height. It is designed to capture how much roundness is concentrated around the trunk, which can be useful alongside traditional body-fat methods.
This result is most useful as a trend metric. Keep measurement technique consistent and track direction over time rather than chasing one isolated reading.
BRI Formula Used
This calculator uses the standard BRI equation with waist and height in the same units (internally centimeters):
BRI = 364.2 - 365.5 x sqrt(1 - ((waist / (2 x pi))^2) / ((0.5 x height)^2))
Because the formula uses a ratio-like geometry term, imperial and metric inputs are both valid as long as waist and height use matching units.
How To Measure Inputs Consistently
- Measure height without shoes against a wall.
- Measure waist at navel level after a normal exhale.
- Keep the tape level and snug without compressing skin.
- Take 2 to 3 readings and use the average.
- Repeat at similar time of day and hydration state.
How To Interpret BRI Alongside Other Metrics
BRI is not a diagnosis. It is a practical indicator of waist-centered roundness that can help contextualize body-fat tracking.
For related waist-height estimation, compare with the RFM Calculator. For a hip-height alternative, compare with the BAI Calculator. For a broader risk-screening estimate, add the Visceral Fat Calculator. For proportion-based silhouette context, compare with the Body Shape Calculator or the Body Shape Analyzer.
To separate lean-mass progress from fat trends, pair BRI with the Lean Body Mass Calculator and FFMI Calculator.
Limitations
BRI depends on tape-measure precision and assumes typical body geometry. It does not directly measure fat tissue and can still miss individual differences in frame size, muscle mass, and fat distribution.
Use BRI with photos, performance markers, and other composition tools for stronger context.
References
- Thomas DM, et al. Relationships between body roundness with body fat and visceral adipose tissue.PubMed record
- Krakauer NY, Krakauer JC. A new body shape index and risk association.PubMed record
- CDC guidance for adult BMI category interpretation:CDC BMI Categories