BAI Calculator (Body Adiposity Index from hip and height)

Understanding the body adiposity index (BAI) calculator — concept and principle

This calculator estimates body fat percentage with the body adiposity index (BAI), which uses only hip circumference and height. It needs no scale, so it can be used where weighing is difficult. People curious about body composition and students use it alongside other measures.

Hip and height, no scale needed — with the default inputs: 27.9% body fat.

How it is calculated

BAI (% body fat) = hip circumference (cm) ÷ height (m)^1.5 − 18
The page also shows hip ÷ height^1.5 before subtracting 18
Hip circumference is measured around the widest part of the buttocks

The principle

Bergman and colleagues (2011) looked for a simple index that tracks body fat measured by dual-energy X-ray absorptiometry (DXA). Hip circumference reflects fat stored around the hips, and dividing by height to the power 1.5 adjusts for body size. They derived the formula in Mexican-American adults and checked it in African-American adults, where it correlated with DXA body fat at R = 0.85. Because it was developed in two specific populations, the result is a rough estimate for anyone else.

Worked example

Defaults: hip 100 cm; height 168 cm.

Height^1.5 = 1.68^1.5 = 2.1775.
Hip ÷ height^1.5 = 100 ÷ 2.1775 = 45.9.
BAI = 45.9 − 18 = 27.9% body fat.

How to read the result

Compare the estimate with other measures rather than relying on it alone. Later studies in other groups found BAI less accurate than hoped, often over- or underestimating fat at the extremes and differing by sex. Healthy body fat ranges depend on age and sex, so ask a health professional for context.

Common mistakes

Measuring the waist instead of the hips.
Pulling the tape too tight or holding it at an angle.
Using height in centimetres in the power term; it must be in metres.
Treating the result as a precise body fat measurement.

Keep in mind: Not a diagnosis. Body fat estimates from formulas can differ substantially from laboratory measurements.

Frequently asked questions

How accurate is BAI?

It correlated well with DXA in the original study, but later research found larger errors in other populations.

Why use height to the power 1.5?

The authors found that this exponent best adjusted hip size for body size.

Is BAI better than BMI?

Not clearly; both are simple estimates with limitations.

Sources: Bergman RN, Stefanovski D, Buchanan TA et al., "A better index of body adiposity", Obesity (Silver Spring) 2011;19(5):1083–1089

Checked 9 Nov 2026. Bergman RN, Stefanovski D, Buchanan TA et al., “A better index of body adiposity”, Obesity (Silver Spring) 2011;19(5):1083–1089 (abstract via University of Pennsylvania ScholarlyCommons); units as stated in Lichtash CT et al., PLoS ONE 2013;8(6):e65954.

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