What is an Ideal BAI?

For women aged between 20 and 39, a BAI value of between 21% and 33% is considered healthy. The healthy range for men in the same age group is between 8% and 21%. For both men and women, the healthy range shifts upwards as they get older.

What is the difference between BAI and BMI?

The BMI uses body weight and height which can lead to muscular people being misclassified as overweight. The BAI uses hip circumference and height and does not require body weight. It aims to estimate body fat more directly.

Is the body adiposity index (BAI) accurate?

It is only a rough estimate. Studies have shown that it tends to overestimate the body fat percentage of lean people and underestimate the body fat percentage of those with higher body fat, making it less accurate than BMI. Use it as one of several indicators.

How do I measure my hip circumference?

Wrap a tape measure around your hips and buttocks at their widest point. Make sure the tape measure is always horizontal and fits snugly against your body but not too tight. To get the most consistent measurements possible, try to wear minimal clothing when measuring.

Can Body Adiposity Index replace body fat measurement?

No. Methods such as DEXA or underwater weighing are much more accurate. The BAI is a quick estimate that can be done with a tape measure and it does not replace a clinical examination.

BAI Calculator (Body Adiposity Index)

Your measurements

Biological sex

Male

Female

Age (years)

Height

Hip circumference

Compare with BMI

Add your weight to compare BAI with your BMI and a BMI-based body-fat estimate.

Body Adiposity Index (% body fat)

Enter your height and hip circumference to estimate your body fat.

Please input values into the fields

Visual breakdown

These visuals update as you enter your measurements.

The body adiposity index (BAI) allows for the estimation of body fat percentage using only hip circumference and height measurements. Unlike the body mass index (BMI), it does not require a scale or weight measurements. The result is presented as a single number that can be directly interpreted as body fat percentage.

What is the body adiposity index?

This index was proposed by Richard Bergman and colleagues in 2011 in the publication "A Better Index of Body Adiposity". The researchers were looking for a simple method to measure on site that would allow them to estimate body fat percentage of different populations without having to incur the cost of laboratory scans.

Methods for directly measuring body fat such as DXA scans or underwater weighing are accurate but expensive and difficult to perform. In contrast, hip circumference and height can be measured with a tape measure in just a few seconds. The original study showed that these two data points were close enough to the amount of body fat measured by DXA to be useful.

The formula for the BAI is as follows:

The BAI is calculated using hip circumference in centimeters and height in meters.

\text{BAI} = \frac{\text{hip circumference (cm)}}{\text{height (m)}^{1.5}} - 18

The value of 1.5 reflects that body proportions do not change linearly with height. Subtracting 18 adjusts this ratio to a scale of body fat percentage. As an example, consider a person who is 1.80 m tall and has a hip circumference of 102 cm.

\text{BAI} = \frac{102}{1.80^{1.5}} - 18 = \frac{102}{2.4149} - 18 \approx 24.2\%

The table below shows each symbol and its example values.

Symbol	Meaning	Example
Hip	Hip circumference in centimetres	102
Height	Standing height in metres	1.80
1.5	Height exponent	fixed
18	Offset constant	fixed
BAI	Estimated body fat percentage	24.2

How to measure your hip and height:

To measure your hip circumference, stand sideways and identify the widest point of your hips and buttocks. Wrap a tape measure around this area once. The tape should be held horizontally at all times and fit snugly against your body but not cut into you. Write down the measurement in either centimeters or inches.

To measure your height, take off your shoes, stand with your back to a wall, align your heels and look straight ahead. If you want to track changes over time, it is best to measure at the same time each day as your height can vary slightly throughout the day.

Interpretation of results.

Your BAI score is compared to the reference values published by Gallagher et al for different age groups and genders. Based on these categories, your results are classified into one of four ranges: underweight, normal weight, overweight, or obese. As women have a higher requirement for essential fatty acids than men, the healthy range is higher for women. With increasing age, the reference ranges shift upwards for both men and women.

The BAI range for healthy women.

Age	Underweight	Healthy	Overweight	Obese
20 to 39	Below 21%	21% to 33%	33% to 39%	Above 39%
40 to 59	Below 23%	23% to 35%	35% to 41%	Above 41%
60 to 79	Below 25%	25% to 38%	38% to 43%	Above 43%

The healthy BAI range for men.

Age	Underweight	Healthy	Overweight	Obese
20 to 39	Below 8%	8% to 21%	21% to 26%	Above 26%
40 to 59	Below 11%	11% to 23%	23% to 29%	Above 29%
60 to 79	Below 13%	13% to 25%	25% to 31%	Above 31%

Comparison of BAI and BMI.

The body mass index (BMI) is calculated from weight and height, and reacts to both muscle and fat. Lean muscular athletes can have a BMI in the overweight range despite having low body fat. The BAI does not take weight into account at all, so it has been suggested as a complementary indicator.

If you enable the BMI comparison feature in the calculator and enter your weight, next to the BMI a body fat percentage estimate based on the BMI will be shown. This estimate uses Deurenberg's formula. By comparing both methods, you can see how different results for the same person can be.

Limitations of the BAI Index

The BAI is an estimate, not a measurement. Subsequent assessments have been more rigorous than the original studies. Freedman and colleagues found that the BAI was no more accurate than BMI or simple hip circumference measurements. A systematic review by Cerqueira et al reported greater error in individual subjects.

As a consistent trend, the BAI has been shown to tend to over-estimate body fat percentage for lean populations, i.e. those with 20% or less body fat. Conversely it tends to under-estimate body fat percentage in people with 30% or more body fat. Use your values in combination with other measurements as a rough guide and do not consider them accurate.

This calculator is provided for general educational purposes only and does not constitute a medical diagnosis or replace the advice of a qualified professional. Please consult with your doctor regarding your body composition and health status.

Frequently asked questions

What is an Ideal BAI?: For women aged between 20 and 39, a BAI value of between 21% and 33% is considered healthy. The healthy range for men in the same age group is between 8% and 21%. For both men and women, the healthy range shifts upwards as they get older.
What is the difference between BAI and BMI?: The BMI uses body weight and height which can lead to muscular people being misclassified as overweight. The BAI uses hip circumference and height and does not require body weight. It aims to estimate body fat more directly.
Is the body adiposity index (BAI) accurate?: It is only a rough estimate. Studies have shown that it tends to overestimate the body fat percentage of lean people and underestimate the body fat percentage of those with higher body fat, making it less accurate than BMI. Use it as one of several indicators.
How do I measure my hip circumference?: Wrap a tape measure around your hips and buttocks at their widest point. Make sure the tape measure is always horizontal and fits snugly against your body but not too tight. To get the most consistent measurements possible, try to wear minimal clothing when measuring.
Can Body Adiposity Index replace body fat measurement?: No. Methods such as DEXA or underwater weighing are much more accurate. The BAI is a quick estimate that can be done with a tape measure and it does not replace a clinical examination.

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Disclaimer: This calculator is provided for general informational and educational purposes only. Our calculators are under active development, and results may be inaccurate, incomplete, or unsuitable for your situation. Always verify the figures independently and seek advice from a qualified professional before relying on them. We make no warranties and accept no liability for any loss or decision arising from use of this tool.

References

Bergman RN et al. A Better Index of Body Adiposity. Obesity (2011)
The original study that introduced the Body Adiposity Index.
Gallagher D et al. Healthy percentage body fat ranges. Am J Clin Nutr (2000)
Source of the age- and sex-specific body-fat classification bands.
Freedman DS et al. The body adiposity index is not more accurate than BMI. Obesity (2012)
Comparison of BAI accuracy against BMI and circumference measures.
Cerqueira MS et al. Validity of the Body Adiposity Index. Adv Nutr (2018)
Systematic review of BAI accuracy for predicting body fat.
Body Adiposity Index — Wikipedia
Overview of the index, its derivation, and criticism.