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How to Calculate and Use the Body Adiposity Index (BAI)

The Body Adiposity Index (BAI) is a measure designed to estimate a person’s percentage of body fat. It can be used alone or in conjunction with other popular and widely used methods for monitoring body composition like the body mass index (BMI), waist-to-hip and waist-to-height ratios. However, none of these techniques, including the body adiposity index, offer precise measures of body fat and body composition, but they are often used for basic testing because they are easy to perform and inexpensive.

Direct measurements of body fat are not possible on a living person since fat surrounds various body tissues. Although many people regularly weigh themselves to determine whether or not their fat level increased, this technique actually reveals very little about changes in their body composition. People can lose weight due to factors such as decreased muscle mass or bone density. And vice-versa, people whose weight has increased may wrongly assume they have gotten fatter, when in fact they have merely added muscle mass.

You can calculate your body adiposity index by dividing your hip circumference in centimetres by your height in metres to the power of 1.5 and then deducting 18. Alternatively, instead of calculating your height in metres to the power of 1.5, you can multiply your height in metres by square root of your height in metres.

BAI estimation formula:

Body Adiposity Index = (Hip Circumference in centimetres / Height in metres ^ 1.5) – 18

This is the same as:

Body Adiposity Index = (Hip Circumference in centimetres / Height in metres × Square Root of Height in metres) – 18

* Please note that when using imperial units, feet need to be entered in decimal points, e.g. 5 foot 11 inch equals 5.9 feet (i.e. 5 + 11/12).

The BAI formula, unlike other formulae used to estimate the percentage of body fat such as the body mass index (BMI), does not use your actual weight. It is based on the assumption that the person’s percentage of fat is linked to the size of their hips relative to their height. Once you know your BAI, the table below will help you determine whether you are a healthy weight or not, depending on your age and gender.

 

Body Adiposity Index Classifications for Women
Age (years) Under weight Healthy Over weight Obese
20 – 39 Less than 21% 21% to 33% Greater than 33% Greater than 39%
40 – 59 Less than 23% 23% to 35% Greater than 35% Greater than 41%
60 – 79 Less than 25% 25% to 38% Greater than 38% Greater than 43%
Body Adiposity Index Classifications for Men
Age (years) Under weight Healthy Over weight Obese
20 – 39 Less than 8% 8% to 21% Greater than 21% Greater than 26%
40 – 59 Less than 11% 11% to 23% Greater than 23% Greater than 29%
60 – 79 Less than 13% 13% to 25% Greater than 25% Greater than 31%

It is hard to tell which of the basic measurements of body composition mentioned above offers the most precise results. Therefore, experts usually use more than one technique, such as the body mass index in combination with the body adiposity index. You can use the BAI & BMI Comparison Calculator below to see how these measures differ in your particular case.

* Please note that when using imperial units, feet need to be entered in decimal points, e.g. 5 foot 11 inch equals 5.9 feet (i.e. 5 + 11/12).

See also: Calculating the Basal Metabolic Rate (BMR)