What is Body Adiposity Index (BAI)? A Detailed Guide

The BAI calculator is a practical tool for anyone who wants to keep their body healthy and fit. With this calculator, you can estimate your body fat percentage and manage your weight more consciously. Read on to learn what BAI is, how body fat percentage is calculated, and the ranges for underweight, healthy, overweight, and obese categories.

⚠️ Important Notice: We strive to make our calculators as accurate and reliable as possible. However, this tool cannot replace a professional medical evaluation. All information on this site is for informational purposes only and should not be considered medical advice. Always share your results with a healthcare professional.

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What is BAI?

BAI stands for Body Adiposity Index. This index estimates the total amount of fat in your body.

The most notable feature of BAI is that it does not use body weight. It only uses your height (in meters) and hip circumference (in centimeters) for calculation. This makes it a fairer assessment tool than BMI (Body Mass Index), especially for individuals with high muscle mass, such as athletes.

Population-based studies have shown that BAI provides approximately equivalent results for body fat percentage across adult men and women of different ethnicities.

Research indicates that BAI’s accuracy in estimating fat is comparable to other anthropometric methods, such as BMI, waist circumference, or hip circumference. For more information, you can check our Waist-to-Hip Ratio Calculator.

Note: No anthropometric method, including BAI, can measure body fat precisely. These methods are easy to use and cost-effective, primarily for screening purposes.

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How is BAI Calculated?

BAI is calculated using the same formula for both men and women:

$$\text{BAI} = \frac{\text{Hip Circumference (cm)}}{\text{Height (m)}^{1.5}} – 18$$

📏 How to Measure Correctly

Hip circumference should be measured at the widest part of the hip bones and below the buttocks (from a side view).
The measuring tape should be flat and snug but not compress the skin.

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Example Calculation

42-year-old male:

• Height: 180 cm → 1.80 m

• Hip circumference: 102 cm

$$\text{BAI} = \frac{102}{1.80^{1.5}} – 18 \approx 24.2\%$$

This result places him in the “overweight” category for men aged 20–39.

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How to Interpret BAI Results

The classification below was developed by Gallagher, Heymsfield, and colleagues, based on age and sex:

👩 Women – BAI Classification

Age	Underfat	Healthy	Overfat	Obese
20–39	<21%	21–33%	>33%	>39%
40–59	<23%	23–35%	>35%	>41%
60–79	<25%	25–38%	>38%	>43%

👨 Men – BAI Classification

Age	Underfat	Healthy	Overfat	Obese
20–39	<8%	8–21%	>21%	>26%
40–59	<11%	11–23%	>23%	>29%
60–79	<13%	13–25%	>25%	>31%

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Is BAI Sufficient? When Are Additional Tests Needed?

BAI can be a promising alternative to BMI, but it has limitations:

• It does not fully account for muscle and bone structure, ethnicity, or age.

• For precise body fat measurement, methods like DEXA, bioelectrical impedance, or skinfold thickness are more appropriate.

Therefore, do not interpret BAI results in isolation. A healthcare professional should evaluate these results together with other body measurements and your overall health status.