Body composition

Body roundness index (BRI) calculator

Calculate the adult body roundness index from standing height and waist circumference. See the formula and measurement limits.

Free · No account neededMethod & sources

YOUR INPUTS

Your measurements

Measurement units

Measure at the top of the hip bone after a normal breath out. Use the same location for later comparisons.

Tape line
Find the top edge of the hip bone at your side. Wrap a level tape just above that edge. Read it after a normal breath out, without pulling the tape into the skin. The diagram is schematic. NHANES waist measurement steps

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YOUR RESULT

Start with your numbers.

Complete the fields to see the calculation, method, and limits.

UNDERSTAND THE METHOD

How to use this calculator

Measure standing height and waist circumference. Enter both in the selected unit system. The original adult research used waist measurements at the top of the hip bone. For a hypothetical person with height 170 cm and waist 85 cm, the waist-to-height ratio is 0.50. The formula gives a BRI of about 3.36, rounded to two decimal places. Use the same waist landmark when comparing later results.

What the result can tell you

BRI describes body shape using two measurements. It does not measure body fat or visceral fat directly, diagnose disease, or set an individual health target. The cited development samples were adults. This calculator does not provide a child reference or a validated personal risk category. Pregnancy and differences in waist measurement location limit comparisons.

Common questions

What does a BRI result mean?

It describes body shape from waist and height. It is not a body-fat percentage, a diagnosis, or a personal risk category.

Where should I measure my waist?

The source research measured waist at the top of the hip bone. Keep that landmark and your units the same when you compare results.

Sources & limitations2 sources

Sources checked September 12, 2026. These notes identify methods and assumptions. They have not received an independent clinical review.

  1. Thomas and colleagues introduced the geometric body roundness index using height and waist circumference in adult research samples.onlinelibrary.wiley.com
  2. The BRI equation uses 364.2 − 365.5 × √(1 − (waist ÷ (π × height))²), with matching length units.nature.com