About the Body Adiposity Index Calculator
The Body Adiposity Index (BAI) estimates your body fat percentage from only two measurements: hip circumference and height. It was published by Richard Bergman and colleagues in 2011 as an alternative to BMI that needs no scale and aims to read directly as % body fat for adult men and women of different ethnicities. It was developed in Mexican-American adults and validated against DXA scans in African-American adults, where it correlated with measured body fat at R = 0.85.
Enter your height and hip circumference and the calculator returns your BAI (as % body fat), how it compares with the healthy body-fat ranges for your sex and age group, and the hip measurement that would sit in the middle of the healthy range for your height. That makes it handy when a reliable scale is not available, or as a cross-check on other body-fat estimates.
Later studies found BAI tends to overestimate body fat in lean people and men and underestimate it in people with higher body fat, and it is not more accurate than BMI for predicting health outcomes. It is intended for adults; it is not validated for children, pregnancy or very muscular athletes.
With the default inputs, the body adiposity index (≈ % body fat) is 29.9%. Change any value above to recalculate instantly.
How to use the body adiposity index calculator
- 1Choose US or metric units, your sex and your age.
- 2Enter your height.
- 3Measure your hips at the widest part of the buttocks with the tape level, and enter it.
- 4Read your BAI as an estimated % body fat and its category.
- 5Compare with another method, such as a skinfold or body-fat estimate, for a fuller picture.
Formula and method
Bergman et al. (2011) found that hip circumference rises and height falls with body fat percentage, and that dividing hip circumference by height to the power 1.5 and subtracting 18 gave values that matched DXA-measured % body fat across sexes without a separate correction. In US mode your hip and height are first converted to centimetres and metres.
Categories use the healthy % body fat ranges proposed by Gallagher et al. (2000), which link BMI cut-offs of 18.5, 25 and 30 to predicted body fat by sex and age band (20–39, 40–59, 60–79). The target hip size reverses the formula: (target % + 18) × height^1.5.
- BAI
- Body adiposity index, interpreted as % body fat
- hip circumference
- Maximum circumference around the buttocks (cm)
- height
- Standing height (m)
Worked examples
35-year-old woman, 5 ft 5 in, 40-inch hips
Hips of 40 in = 101.6 cm and height of 65 in = 1.651 m. 1.651^1.5 = 2.1214, so BAI = 101.6 ÷ 2.1214 − 18 = 29.9% body fat, inside the 21–33% healthy range for women aged 20–39.
50-year-old man, 178 cm, 104 cm hips (metric)
1.78^1.5 = 2.3748, so BAI = 104 ÷ 2.3748 − 18 = 25.8%. For men aged 40–59 the healthy range is 11% to under 22%, so this falls in the overweight band. A hip size of about 81.9 cm would put him at the middle of the healthy range (16.5%).
68-year-old woman, 5 ft 2 in, 48-inch hips
Height is 62 in = 1.5748 m and hips 48 in = 121.92 cm. 1.5748^1.5 = 1.9762, so BAI = 121.92 ÷ 1.9762 − 18 = 43.7%, above the 42% obesity threshold for women aged 60–79.
Frequently asked questions
How accurate is the body adiposity index?+
In the validation study BAI correlated with DXA body fat at R = 0.85. Later research found typical errors of several percentage points, with overestimation in lean people and men and underestimation at high body fat, so it is a rough estimate rather than a measurement.
Is BAI better than BMI?+
BAI estimates % body fat directly and needs no scale, which is its main advantage. However, large studies have not shown it predicts disease or mortality better than BMI or waist-based measures, so it is best used as a complement.
Where do I measure hip circumference for BAI?+
Measure around the maximum protrusion of the buttocks with the tape horizontal and snug but not compressing the skin, standing with feet together. Wear light clothing or measure on bare skin for consistency.
What is a healthy body fat percentage?+
Using Gallagher’s ranges, healthy body fat for women is roughly 21–33% at ages 20–39 and rises slightly with age, and for men roughly 8–20% at ages 20–39. Athletes are often below these ranges without health problems.
Can BAI be used for children?+
No. BAI was developed and validated in adults. Children and adolescents should be assessed with BMI-for-age percentiles or other age-appropriate methods.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.