Body Adiposity Index (BAI) Calculator
Calculate the original Bergman BAI from height and hip circumference, with DXA validation limits and no automatic body-fat category.
Content updated: View sources
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Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.
About
The Bergman Body Adiposity Index (BAI) uses standing height and hip circumference; body weight is not part of its equation. The original work developed the formula in the BetaGene Mexican-American cohort using DXA body-fat percentage as the reference and tested it in the African-American TARA cohort. It proposed one equation without a numeric sex coefficient, but those cohorts do not represent every population or body-fat level. [1]
The original authors designed the numerical result to approximate percent body fat. Later adult validation found poor individual agreement with DXA and systematic bias, so this page reports the value as an anthropometric index without a percent sign, health grade, obesity diagnosis, target, or treatment recommendation. [2, 3]
Formula
Interpretation
Why this page does not report an exact body-fat percentage
A 2018 systematic review included 19 adult studies using DXA as the reference across regions, ethnicities, both sexes, and ages 18–83. Agreement was poor where concordance was assessed; Bland–Altman analyses showed large individual errors, and sensitivity to body-fat change was limited. BAI tended to overestimate when DXA body fat was 20% or lower and underestimate when it was above 30%. The review did not recommend BAI for determining adult body-fat percentage. [2]
Correlation is not agreement
An index can correlate with DXA across a group while still differing substantially for an individual. Correlation describes how values vary together; it does not prove that two methods are interchangeable. A comparison of 1,151 healthy adults found BAI was not more accurate than BMI, waist circumference, or hip circumference, while a DXA study in adults with overweight or obesity found significant underestimation despite a strong correlation. Group averages therefore cannot guarantee personal accuracy. [3, 4]
BAI does not replace DXA, a four-compartment model, CT, MRI, or another appropriately validated body-composition method.
Hip measurement protocol
WHO STEPS measures the maximum circumference over the buttocks with the person standing, feet together, weight evenly distributed, and arms relaxed. The tape should remain horizontal and snug without constricting; thick or bulky clothing should be removed. For repeated measurements, keep the anatomical level, posture, clothing, and tape tension consistent. [5]
Hip circumference is not waist circumference, the iliac-crest waist site, the narrowest waist, the navel, or a greater-trochanter landmark used by some studies. Changing the site changes the formula numerator and can make results incomparable.
BAI compared with other anthropometric measures
| Measure | Inputs | Output | Why it is not interchangeable with BAI |
|---|---|---|---|
| BAI | Hip, height | Bergman anthropometric index | Limited individual agreement with DXA |
| BMI | Weight, height | Weight-height index | Does not estimate fat proportion directly |
| Hip circumference | Hip | Single external circumference | Not scaled by height |
| WHR | Waist, hip | Distribution ratio | Uses waist as numerator and hip as denominator |
| WHtR | Waist, height | Central-adiposity ratio | Uses waist rather than hip |
| RFM | Waist, height, published sex variable | Regression body-fat estimate | Different inputs, model, and validation |
| BRI | Waist, height | Thomas geometric index | Not a body-fat-percentage regression |
No one measure in this table is universally best for every population, purpose, or clinical decision. [2, 3]
Situations outside a simple BAI interpretation
Children and adolescents, pregnancy, marked edema or ascites, unusual hip or lower-limb anatomy, amputation, inability to stand consistently, a changed hip-measurement site, unusual muscle or fat distribution, and very low or high body fat can reduce comparability or extend beyond the original adult cohorts. These are validation and measurement limits, not absolute contraindications. The calculator cannot detect them and does not diagnose obesity or metabolic disease or select weight-loss, diet, exercise, medication, or treatment goals. [1, 2, 5]
Worked arithmetic examples
Metric: Height 170 cm and hip circumference 95 cm give 95 ÷ 1.7^1.5 − 18 = 24.859808200294232, displayed as 24.86.
Exact US equivalence: 170 ÷ 2.54 inches and 95 ÷ 2.54 inches produce the same raw result after exact normalization. [6]
Larger hip circumference: At the same height, increasing the submitted hip circumference increases BAI because hip circumference is the equation numerator. That is arithmetic, not a health grade.
Blank, zero, negative, exponent-form, nonnumeric, nonfinite, or technically unsupported inputs produce no result. Scientific notation is deliberately rejected so the complete submitted decimal is unambiguous.
References
- Bergman RN, Stefanovski D, Buchanan TA, et al. A Better Index of Body Adiposity. Obesity (Silver Spring). 2011;19(5):1083–1089. PMID 21372804. PMCID PMC3275633. doi:10.1038/oby.2011.38.
- Cerqueira MS, Santos CA, Silva DAS. Validity of the Body Adiposity Index in Predicting Body Fat in Adults: A Systematic Review. Adv Nutr. 2018;9(5):617–624. PMID 30239583. PMCID PMC6140443. doi:10.1093/advances/nmy043.
- Freedman DS, Thornton JC, Pi-Sunyer FX, et al. The Body Adiposity Index Is Not a More Accurate Measure of Adiposity Than Is BMI, Waist Circumference, or Hip Circumference. Obesity (Silver Spring). 2012;20(12):2438–2444. PMID 22484365. PMCID PMC3477292. doi:10.1038/oby.2012.81.
- Triana-Reina HR, Ramírez-Vélez R. Predictive Validity of the Body Adiposity Index in Overweight and Obese Adults Using Dual-Energy X-ray Absorptiometry. Nutrients. 2016;8(12):737. PMID 27916871. PMCID PMC5188406. doi:10.3390/nu8120737.
- World Health Organization. WHO STEPwise Approach to Surveillance (STEPS) Manual. Part 3, Section 5: Measuring Hip Circumference. Updated 26 January 2017.
- National Institute of Standards and Technology. NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.
FAQ
BAI = hip circumference in centimeters ÷ height in meters raised to 1.5 − 18. This page normalizes units before applying that equation and keeps the raw calculation unrounded until display.
Sources: [1]
The formula was developed in the BetaGene Mexican-American cohort and tested in the African-American TARA cohort using DXA body-fat percentage as the reference. Those cohorts do not establish equal accuracy in every population.
Sources: [1]
Across 19 adult DXA studies, agreement was poor where assessed, individual errors were wide, and sensitivity to body-fat change was limited. BAI tended to overestimate at 20% body fat or less and underestimate above 30%.
Sources: [2]
BAI uses hip circumference and height, whereas BMI uses weight and height. A direct adult comparison did not find BAI more accurate than BMI, waist circumference, or hip circumference for estimating DXA body fat.
Sources: [3]
WHO STEPS measures the maximum circumference over the buttocks while standing with feet together, weight evenly distributed, arms relaxed, and the tape horizontal and snug without constricting.
Sources: [5]
Yes, when the measurements are exactly equivalent. The calculator converts each inch to exactly 2.54 centimeters and then applies the same centimeter-and-meter formula without intermediate rounding.
Sources: [6]
No. BAI is neither a diagnosis nor a complete clinical assessment. It cannot establish obesity, diabetes, metabolic syndrome, cardiovascular disease, or another condition.
Sources: [2]
No. This calculator does not select a body-fat goal, diet, exercise program, weight-loss target, medication, referral, monitoring schedule, or treatment.
Sources: [2]
Related Calculators
Fat-Free Mass
Estimate adult fat-free mass with the Boer equation and derive FFMI from height using metric or US units.
RFM
Estimate adult whole-body fat percentage from height and waist circumference using the published Woolcott–Bergman RFM equation.
WHR
Calculate adult waist-to-hip ratio from standardized waist and hip circumferences in metric or US units.
Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.