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Body Adiposity Index (BAI) Calculator

Estimate body fat percentage without a scale using your hip and height.

How it is calculated

The index is BAI = hip / heightm1.5 − 18. Hip is the circumference at the widest point in centimetres, and height is entered in centimetres too; the tool divides it by 100 to get metres before applying the 1.5 power. The result is shown as a percentage. The category depends on the sex selected, because the cut-offs differ. For women: below 21 underweight, 21 to under 33 healthy, 33 to under 39 overweight, 39 and above obese. For men: below 8 underweight, 8 to under 21 healthy, 21 to under 26 overweight, 26 and above obese. Zero, negative or empty values give no result. Weight is not used at all.

Worked example

A woman with a 100 cm hip and a height of 165 cm. Height in metres is 1.65, and 1.65 raised to the power 1.5 is about 2.1195. Dividing 100 by 2.1195 gives 47.18, and subtracting 18 leaves 29.18%. For a woman, 29.18 sits between 21 and 33, so the tool labels it Healthy. The same measurements with male selected give 29.18% as well, but the male table places it in the Obese band.

Try this example →

Common mistakes

  • Entering height in metres (1.65). The field takes centimetres, and 1.65 produces a meaningless result in the tens of thousands of percent.
  • Measuring the waist or the belt line instead of the hip. The formula needs the widest circumference around the buttocks.
  • Leaving the sex on the default, male. The same BAI falls in a different category for women, so the label can be wrong by two bands.
  • Reading the number as a measured body-fat test. It is an estimate from two measurements, so treat the category as a rough guide.
  • Measuring the hip over thick clothing, which adds centimetres directly into the result.

Sources

About this calculator

This calculator estimates body fat percentage using the Body Adiposity Index (BAI), developed by Bergman et al. in 2011: BAI = (hip circumference / height^1.5) − 18, with hip in cm and height in meters. Unlike BMI, it doesn't require body weight at all — only hip circumference and height, which makes it useful when a reliable scale isn't available or when muscle mass would skew a weight-based estimate.

Researchers and fitness professionals use BAI as a quick screening tool, though it was validated mainly on Mexican-American and African-American adult populations and tends to be less accurate for very muscular people or extreme heights.

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  • Editorial team

    Measurement technique matters more than it seems. At a height of 165 cm, every extra centimetre of hip adds about 0.47 percentage points to the result, so a tape pulled tight or held at a slightly different spot can shift it by a point or two, enough to cross a category line. If you are tracking change, use the same tape, the same position and light clothing each time. Do your own repeated measurements land close together? Share the spread you see.

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