Comprehensive Calculator Guide
A Body Shape Index (ABSI) measures belly fat relative to your weight and height, then compares you with people of your age and sex. A 40-year-old man, 178 cm, 85 kg, with a 95 cm waist has an ABSI of 0.0795 against an average of 0.0809 for his age: a z-score of −0.38, low risk. Two people with the same BMI can differ a lot on ABSI, because the waist makes the difference.
What it measures and how to read it
Nir and Jesse Krakauer proposed ABSI in 2012, dividing the waist by what BMI and height would predict. What remains is waist the body size doesn’t explain — excess belly fat — and in data on over 14,000 US adults it predicted mortality independently of BMI.
The calculator compares your ABSI with the NHANES average and standard deviation for your age and sex. Risk bands by z-score: below −0.868 very low, to −0.272 low, to 0.229 average, to 0.798 high, above that very high.
How to Use
- Choose your sex and enter your age (18–85).
- Enter your height, weight and waist at the navel.
- Press “Calculate ABSI” to see your index, your age average, your z-score and its risk band.
Formula Used
ABSI = waist (m) ÷ (BMI^(2/3) × √height (m)) | z = (ABSI − age-and-sex mean) ÷ SD
Practical Examples
- Example 1
- Man, 40, 178 cm, 85 kg, waist 95 cm: ABSI 0.0795, mean 0.0809, z −0.38 (low).
- Example 2
- Woman, 35, 165 cm, 68 kg, waist 86 cm: ABSI 0.0784, mean 0.0778, z 0.12 (average).
Important Tips
- Track the z-score rather than the raw index; it allows for your age.
Common Mistakes to Avoid
- Comparing raw ABSI values between people of different ages or sexes.
Frequently Asked Questions
- What is A Body Shape Index?
- A belly-fat measure from waist, BMI and height, compared with the average for your age and sex.
- What is a normal ABSI?
- Around 0.08, rising with age; a z-score between −0.27 and 0.23 means average risk.
- How is it different from BMI?
- BMI relates weight to height; ABSI measures waist beyond what that weight and height predict.