Quick guide
How to use this calculator
- Use the labels and unit notes to enter the requested measurement, date, time, or observation exactly as recorded.
- Check the visible method, population, and unit basis before using the result; switch modes rather than converting values mentally.
- Read the calculation audit and limitations together. The result supports measurement or tracking and does not replace diagnosis, treatment, or urgent medical assessment.
Calculation method
How the body roundness index calculator works
BRI = 364.2 - 365.5 × sqrt[1 - (waist/(2π))² / (0.5×height)²], with height and waist in the same unit.
BRI is a dimensionless geometric index derived from an ellipse model of the body. This page reports the index and waist-to-height ratio only.
Worked example
Body Roundness Index example
A height of 170 cm and waist of 80 cm produce a BRI of approximately 2.82.
BRI = 364.2 - 365.5 × sqrt[1 - (waist/(2π))² / (0.5×height)²], with height and waist in the same unit.
Supported inputs
Precision and limits
Supported purpose
The calculator does not translate BRI into body-fat percentage, mortality, disease risk, diagnosis, or a treatment target. Pregnancy and measurements that violate the equation geometry are excluded.
Measurement quality
The output is only as reliable as the entered measurement, device, timing, units, and applicable reference population. Recheck unexpected values against the original record.
Clinical boundary
This calculator does not diagnose a condition, choose treatment, change medication, or determine that an urgent symptom is safe to monitor at home. Contact an appropriate health professional or local emergency service when the situation may be urgent.
Privacy
Entered health values and results stay in this browser tab. They are not placed in URLs, analytics, logs, local storage, session replay, or a cloud record by this calculator.
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