This tool shows you how to calculate ABSI, A Body Shape Index, from waist, height and weight, then compares it with an adult reference value to give a z-score and a plain-English band. It gives a waist-based view that BMI alone cannot.
ABSI = waist (m) ÷ (BMI^(2/3) × height (m)^(1/2)), from Krakauer and Krakauer (2012). If you leave the reference mean and SD blank, the calculator uses 0.0808 and 0.0053, an all-adult average; age- and sex-specific tables in the original research give a more precise z-score. Bands are quintiles of a normal distribution. Educational only, not a diagnosis.
How Do You Calculate ABSI?
Divide your waist in metres by BMI^(2/3) × √height in metres. For a 90 cm waist, 175 cm height and 75 kg: BMI is 24.49, BMI^(2/3) × √1.75 = 11.156, and 0.9 ÷ 11.156 = 0.08067. Against the default reference (0.0808, SD 0.0053) that is a z-score of −0.02, in the average band.
- Work out BMI: 75 ÷ 1.75² = 24.49.
- Raise BMI to the power 2/3 (8.433) and multiply by √1.75 (1.323) to get 11.156.
- Divide the waist in metres by that: 0.9 ÷ 11.156 = 0.08067.
- Find the z-score: (0.08067 − 0.0808) ÷ 0.0053 ≈ −0.02.
ABSI vs BMI: Why the Index Exists
ABSI tells you whether your waist is large for your build, which BMI cannot. BMI can’t tell a muscular person from someone carrying weight around the middle. A Body Shape Index, published by Nir and Jesse Krakauer in 2012, asks how large your waist is compared with what would be expected for your height and BMI. Because the expected waist is built into the denominator, ABSI is almost independent of BMI: two people with the same BMI can have very different scores. The raw number is always a small decimal around 0.08, so the tool turns it into a z-score that is easier to read.
Formula: BMI = Weight (kg) ÷ Height (m)^2. ABSI = Waist (m) ÷ (BMI^(2/3) × Height (m)^(1/2)). ABSI z-score = (ABSI − Reference mean) ÷ Reference SD. Bands: below −0.842 very low, −0.842 to −0.253 low, −0.253 to 0.253 average, 0.253 to 0.842 high, above 0.842 very high.
- Units: metric (cm, kg) or US (inches, pounds); fields convert when you switch.
- Waist circumference: measured around the bare abdomen, midway between the lowest rib and the top of the hip bone, after a normal breath out.
- Height: standing, without shoes.
- Weight: light clothing, ideally in the morning.
- Reference mean and Reference SD: the comparison values for the z-score. If you leave them blank, the calculator uses 0.0808 and 0.0053, an all-adult average; enter age- and sex-specific values if you have them, for example when using it as a body shape index calculator for women.
Example Scenarios
| Waist (cm) | Height (cm) | Weight (kg) | BMI | ABSI | z-score | Band |
|---|---|---|---|---|---|---|
| 90 | 175 | 75 | 24.5 | 0.08067 | −0.02 | Average |
| 80 | 162 | 60 | 22.9 | 0.07803 | −0.52 | Low |
| 102 | 180 | 95 | 29.3 | 0.07995 | −0.16 | Average |
| 70 | 165 | 55 | 20.2 | 0.07347 | −1.38 | Very low |
| 93 | 168 | 72 | 25.5 | 0.08280 | +0.38 | High |
| 105 | 168 | 80 | 28.3 | 0.08714 | +1.20 | Very high |
ABSI Z Score Meaning and Normal Range
A z-score between −0.253 and 0.253 is average; raw ABSI for adults usually sits between about 0.07 and 0.09. Look at rows three and six. The first person has the higher BMI, yet the second has the higher ABSI because more of their weight sits at the waist. In the original study a higher ABSI z score was associated with higher mortality in a large US survey sample, independent of BMI, but an association in a population is not a personal prediction.
- Measure the waist carefully. A 2 cm error moves ABSI by about 2%, which shifts the z-score by roughly 0.3 at typical values.
- ABSI rises with age, so an all-adult reference will flag many older adults as high. Age- and sex-specific reference values give a fairer comparison.
- ABSI vs waist to hip ratio: both target central fat, but the hip ratio needs a second tape measurement while ABSI uses height and weight you probably already know.
- The index has been studied mostly in adults; do not use it for children or during pregnancy.
The ABSI calculator is educational. If your waist is growing or you are worried about heart or metabolic risk, talk to your doctor, who can check blood pressure, blood sugar and cholesterol. For the derivation and research background, see Wikipedia’s article on the body shape index.
Common questions about A Body Shape Index
How do you calculate ABSI?
Divide waist circumference in metres by BMI to the power of two-thirds multiplied by the square root of height in metres. For a 90 cm waist, 175 cm and 75 kg, that is 0.9 ÷ 11.156 = 0.08067. The formula was introduced by Krakauer and Krakauer in 2012.What is the normal range for A Body Shape Index?
Raw ABSI is a small number, usually between about 0.07 and 0.09 for adults. On the z-score scale used here, −0.253 to 0.253 counts as average.What does an ABSI z score mean?
A z-score near zero means your body shape is close to the reference average. Negative values mean a smaller waist than expected for your height and BMI, and positive values a larger one. In research, higher scores were linked with higher risk, but the score is not a diagnosis on its own.Is this a body shape index calculator for women too?
Yes, the formula is the same for men and women. Average ABSI differs somewhat by sex and age, which is why the reference mean and SD are editable. If you have age- and sex-specific values from the published tables, enter them for a more precise female or male z-score.How is ABSI different from BMI and waist-to-hip ratio?
BMI uses only height and weight. ABSI compares your waist with the waist expected for your height and BMI, and is designed to be almost independent of BMI. Waist-to-hip ratio needs a second tape measurement at the hips.When should I see a doctor about my result?
See a doctor if your waist has grown noticeably, if your score is in the high or very high band and you have other risk factors such as high blood pressure, diabetes or a family history of heart disease, or if you have any symptoms. A clinician can order proper tests.Related Calculators
For other views of body shape, try the waist-to-height ratio calculator and the waist-to-hip ratio calculator. The BMI calculator with weight categories gives the number the ABSI calculator builds on.