HEALTH · BODY ADIPOSITY INDEX (BAI)

Body Adiposity Index (BAI) Calculator

Estimate body fat percentage using the BAI formula (Bergman 2011) from hip circumference and height alone — no weight required. Supports metric and imperial units.

Measurements

e.g. 168 cm

Widest point around the hips

BAI Body Adiposity Index
27.9%
Acceptable
Estimated body fat27.9%
Category (ACE)Acceptable

Formula: BAI = (hip / height1.5) − 18 (Bergman et al., Obesity 2011). The BAI is an estimate — DEXA or hydrostatic weighing provide more accurate results. Only hip circumference and height are needed (no weight required).

About This Calculator

The Body Adiposity Index (BAI) estimates your body fat percentage from just two measurements: hip circumference and height. Unlike BMI, it does not require body weight — and unlike the US Navy body fat formula, it needs only one circumference measurement. Enter your hip and height to get a body fat estimate and ACE fitness category.

How It Works

The BAI formula was published by Bergman et al. in Obesity (2011) after validation against DEXA scans across ethnically diverse populations: BAI = (hip / height^1.5) − 18. Hip is measured in centimeters and height in meters. The result is classified using ACE (American Council on Exercise) body-fat norms: Essential fat, Athletes, Fitness, Acceptable, and Obese.

The Formula

BAI (%) = (hip / height^1.5) − 18

hip
Hip circumference in centimeters (widest point)
height
Height in meters (height_cm / 100)
18
Empirical constant from Bergman (2011) calibration

Frequently Asked Questions

How does the BAI compare to the US Navy body fat formula?
The US Navy formula requires neck, waist, and hip circumferences (plus height), while BAI needs only hip and height. The Navy formula is generally considered more accurate for a broad population. BAI may be preferable when only hip and height are available, but both are estimates — DEXA scanning remains the gold standard.
Why doesn't BAI need body weight?
BAI was developed to estimate body fat without a scale, which can be useful in clinical settings where accurate weight measurement is difficult. The formula was validated against DEXA data and showed good correlation with body fat percentage independent of weight.
Is BAI accurate for all ethnicities?
BAI was initially validated in a racially diverse US cohort (the BioLINCC and IRASFS studies). Subsequent research has found it performs reasonably well across ethnic groups, though some studies show it may underestimate body fat in South Asian individuals. As with all population-level formulas, individual accuracy can vary.