How is BAI calculated?

BAI is calculated using the formula: BAI = (hip circumference in cm ÷ height in m^1.5) − 18. Our calculator lets you enter hip and height in metric or imperial units and converts them automatically.

Is BAI better than BMI?

BAI can be useful when body weight is not available, but research has shown that it is not consistently superior to BMI for predicting health risk. Both are rough screening tools and should not replace a clinical assessment or body composition testing.

What is a healthy BAI?

There is no universally accepted BAI classification, but suggested ranges for adults are roughly: for men, 8–21% normal and 22–26% overweight; for women, 21–33% normal and 34–38% overweight. Values above these ranges may indicate obesity. Always interpret results with caution and in context.

Can I use BAI for children or athletes?

BAI was developed for adults and has not been validated for children, teenagers, pregnant people, or high‑performance athletes. For these groups, more specialized growth charts or body composition methods are recommended.

Body Adiposity Index (BAI) Calculator – Estimate Body Fat from Hip & Height

Q: What is the Body Adiposity Index (BAI)?

The Body Adiposity Index (BAI) is an estimate of body fat percentage based on hip circumference and height. Unlike BMI, it does not use body weight and was proposed as a potentially better indicator of body fat in some populations.

Estimate your body fat percentage using the Body Adiposity Index (BAI), which relies only on hip circumference and height. This tool supports both metric and imperial units and gives an interpretation by sex and age group.

Category	Men (BAI %)	Women (BAI %)
Underfat	< 8	< 21
Normal	8 – 21	21 – 33
Overweight	22 – 26	34 – 38
Obese	> 26	> 38

What is the Body Adiposity Index (BAI)?

The Body Adiposity Index (BAI) is a way to estimate body fat percentage using only hip circumference and height. It was proposed as an alternative to BMI (Body Mass Index), especially when body weight is not available or is difficult to measure.

Unlike BMI, which uses weight and height, BAI is based on the idea that hip size relative to height reflects the amount of body fat stored in the body.

BAI formula

BAI = ( hip circumference in cm ÷ height in m^1.5 ) − 18

Where:

Hip circumference is measured at the widest part of the buttocks.
Height is measured without shoes, in meters.

Our calculator accepts both metric and imperial units and converts them internally to centimeters and meters before applying the formula.

Step-by-step example

Suppose a person has:

Hip circumference = 100 cm
Height = 1.70 m

The calculation is:

height^1.5 = 1.70^1.5 ≈ 2.22
BAI = 100 ÷ 2.22 − 18 ≈ 45.0 − 18 = 27.0%

A BAI of about 27% would typically fall in the overweight range for a man and near the lower end of the obese range for a woman, using the reference table above.

How to measure hip circumference correctly

Stand upright with feet together and weight evenly distributed.
Wrap a flexible tape measure around the widest part of your buttocks.
Ensure the tape is horizontal and snug but not compressing the skin.
Measure over thin clothing or underwear for best accuracy.
Take the measurement to the nearest 0.5–1 cm (or 0.25–0.5 in).

Interpreting your BAI result

There is no single, universally accepted BAI classification. The table used in this calculator is based on approximate ranges suggested in the literature and aligned loosely with common body fat percentage categories for adults:

Underfat – BAI below the normal range for your sex.
Normal – BAI within the suggested healthy range.
Overweight – BAI above normal but below obesity.
Obese – BAI significantly above the normal range.

Keep in mind that age, ethnicity, body shape, and fitness level all influence how body fat is distributed and how risky a given percentage may be.

BAI vs BMI: which is better?

Research has shown that BAI is not consistently superior to BMI for predicting health risks such as cardiovascular disease or diabetes. Key differences:

BMI uses weight and height, is very easy to obtain, but does not distinguish between fat and muscle.
BAI uses hip circumference and height, and can be useful when weight is unknown or unreliable.

In practice, both are screening tools, not diagnostic tests. For a more accurate assessment of body composition, methods such as DEXA, bioimpedance, or skinfold measurements are preferred.

Limitations of BAI

Developed and validated mainly in specific adult populations; may not generalize to all ethnicities.
Not validated for children, teenagers, pregnant people, or elite athletes.
Hip circumference can be measured inconsistently, introducing error.
Does not account for fat distribution (e.g., visceral vs subcutaneous fat).

Always interpret BAI together with other indicators: waist circumference, blood pressure, blood tests, physical fitness, and clinical evaluation.

Health disclaimer

This Body Adiposity Index calculator is for educational purposes only and does not provide medical advice, diagnosis, or treatment. If you are concerned about your weight, body fat, or overall health, consult a qualified healthcare professional.

BAI calculator – FAQ

Can I use BAI to track progress over time?

Yes, BAI can be used as one of several metrics to monitor changes in body composition over weeks or months, especially if you measure hip circumference consistently. However, small day‑to‑day changes are often just measurement noise.

Is BAI accurate for very muscular people?

No simple index is perfect for highly muscular individuals. Like BMI, BAI may overestimate body fat in people with large hip muscles and glutes. In such cases, direct body composition testing is more reliable.

Should I use BAI or BMI for health risk assessment?

Most clinical guidelines and risk charts are still based on BMI and waist circumference. BAI can be a useful additional perspective, especially when weight is unknown, but it should not replace established medical criteria.

Body Adiposity Index (BAI) Calculator

Enter your measurements

Your BAI result

Quick reference (adults)