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BAI Calculator

Health

Calculate your Body Adiposity Index (BAI) from hip circumference and height to estimate body fat percentage instantly without stepping on a scale.

Reviewed by the thecalcu.com team · Last updated August 1, 2026

Gender
Hip Circumference
cm
60200
Height
cm
120220

Measure your hips at their widest point. BAI estimates body fat percentage without needing a scale.

Body Adiposity Index

0.0%
🔵

Very Lean

Bands: <8 very lean, 8–20 athletic, 21–25 fit, 26–30 average, ≥31 obese

For general guidance only.BAI is an estimate — it doesn't account for muscle mass or bone density directly. Consult a healthcare provider for a full body composition assessment.

What is a BAI?

A BAI Calculator computes the Body Adiposity Index, a formula that estimates body fat percentage using only your hip circumference and height, no scale required. Developed as an alternative to BMI-based estimates, BAI was designed to work across different body types and ethnicities using measurements that are simple to take with just a tape measure, making it a practical complement to the BMI Calculator and Body Fat Calculator.

This calculator takes your hip circumference and height, applies the BAI formula, and returns an estimated body fat percentage along with a category label so the result is immediately interpretable.

Why Use a BAI Calculator?

Not everyone has consistent access to a reliable scale, and body fat percentage is often more informative than weight alone when tracking fitness or health goals. BAI fills that gap by estimating body fat from just two measurements, hip circumference and height, giving you a usable body composition estimate without weighing yourself.

This makes BAI particularly useful for spot-checking body composition changes during a fitness program, or as a quick cross-reference alongside your Waist-to-Hip Ratio Calculator result for a fuller picture of body shape and fat distribution.

Who Should Use This Calculator?

  • Anyone without consistent access to a scale who still wants a body fat estimate.
  • People tracking fitness progress who want a metric that complements weight and BMI tracking.
  • Health-conscious individuals curious how their body fat estimate compares across different formulas.
  • Fitness coaches and trainers cross-checking client body composition using multiple simple measurements.
  • Anyone researching body composition metrics who wants to understand how BAI is calculated and interpreted.

What Insights Does the BAI Calculator Give You?

The calculator returns one core figure with a category interpretation:

  • BAI (Body Fat %), the estimated body fat percentage derived from your hip circumference and height using the Krakauer/Bergman formula.
  • Category, Very Lean, Athletic, Fit, Average, or Obese, based on gender-specific bands, giving immediate context to what your BAI score means.

Because the healthy ranges differ meaningfully between men and women, the calculator automatically applies the correct thresholds based on the gender you select.

How to use this BAI calculator

  1. Select your Gender, Male or Female, since BAI category thresholds differ by gender.
  2. Measure your hips at their widest point and enter it as Hip Circumference in centimeters.
  3. Enter your Height in centimeters.
  4. Read your BAI result, shown as an estimated body fat percentage.
  5. Check the category card to see where your BAI falls relative to typical ranges for your gender.
  6. Review the step-by-step breakdown to see exactly how your BAI was calculated.
Show formula & methodology ↓Show less ↑

Formula & Methodology

BAI is calculated directly from hip circumference and height:

BAI = (Hip Circumference in cm ÷ Height in meters^1.5) − 18

Worked example: for a man with a 100 cm hip circumference and 170 cm height:
- Height = 1.70 m
- 1.70^1.5 = 2.217
- BAI = (100 ÷ 2.217) − 18 = 45.1 − 18 = 27.1%
- A BAI of 27.1% falls in the Average category for men under this calculator's approximate bands.

Approximate bands for men: below 8% Very Lean, 8–20% Athletic, 21–25% Fit, 26–30% Average, 31% and above Obese. For women: below 21% Very Lean, 21–32% Athletic, 33–38% Fit, 39–43% Average, 44% and above Obese.

Frequently Asked Questions

What is the Body Adiposity Index (BAI)?
The Body Adiposity Index (BAI) is a formula that estimates body fat percentage using only hip circumference and height, without requiring a body weight measurement. It was developed by researchers in 2011 as an alternative to BMI-based body fat estimates, aiming to work well across different ethnic groups without needing a scale.
How is BAI different from BMI?
BMI uses weight and height to estimate general body size, while BAI uses hip circumference and height to estimate body fat percentage directly, without factoring in weight at all. This makes BAI useful in situations where a scale isn't available, though it should still be viewed as an estimate rather than a precise body fat measurement.
What is the formula for calculating BAI?
BAI = (Hip Circumference in cm ÷ Height in meters^1.5) − 18. This calculator converts your height to meters, applies your hip circumference measurement, and computes the result automatically.
How do I measure my hip circumference for BAI?
Measure around the widest part of your hips and buttocks while standing with your feet together, using a flexible tape measure kept level and snug but not tight. Take the measurement without compressing the skin or pulling the tape too tight.
What is a healthy BAI score?
Healthy BAI ranges differ by gender: for men, roughly 8–20% is considered athletic to fit, and for women, roughly 21–32% is considered athletic to fit, with higher values indicating higher estimated body fat. This calculator applies approximate category bands, Very Lean, Athletic, Fit, Average, and Obese, based on your BAI score and gender.
Is BAI more accurate than BMI for estimating body fat?
Research findings on this are mixed, some studies find BAI correlates well with body fat percentage measured by DEXA scans, while others find it less accurate than BMI in certain populations. BAI is best used as a complementary estimate alongside other measures like the [BMI Calculator](/bmi-calculator/) and [Body Fat Calculator](/body-fat-calculator/), not as a replacement for clinical body composition testing.
Why doesn't BAI use body weight in its formula?
BAI was specifically designed to estimate body fat without a scale, using only a tape measure and a height measurement, which makes it accessible in settings without reliable weighing equipment. This is one of its key practical advantages over weight-based formulas like BMI.
Can BAI be used for athletes or very muscular individuals?
BAI, like most anthropometric formulas, can be less accurate for highly muscular individuals since it doesn't distinguish between muscle and fat directly, it estimates based on population-level relationships between hip size, height, and body fat. Athletes with larger hip circumferences due to muscle mass may see BAI overestimate their actual body fat percentage.
Should I track my BAI over time?
Yes, tracking BAI periodically, such as monthly, can help show trends in estimated body fat that complement changes in weight or BMI, especially during a fitness or weight management program. Combining BAI trends with other measures like the [Waist-to-Hip Ratio Calculator](/waist-hip-ratio-calculator/) gives a fuller picture of body composition change.
What should I do if my BAI result seems high?
A high BAI is a signal to look at your overall body composition and health picture rather than a standalone diagnosis, consider cross-checking with other calculators like body fat percentage and BMI, and consult a healthcare provider for a comprehensive assessment. Lifestyle factors such as diet and physical activity are the primary levers for change over time.
Do I need any special equipment to calculate BAI?
No, you only need a flexible tape measure to record your hip circumference and a way to measure your height, both of which can be done at home without a scale. This calculator handles the BAI formula and category classification automatically once you enter those two measurements.
Also known as
Body Adiposity Index calculatorBAIbody fat estimate calculatorhip to height body fat calculatorBAI score