ABSI Calculator

A Body Shape Index (ABSI) tells you whether your waist is large or small for your height and weight. Two people with the same BMI can carry their weight very differently, and ABSI is built to pick up that difference.

What ABSI Measures

ABSI measures how much of your size sits around your middle, compared with what is typical for your height and weight. A higher ABSI means a more central, apple-like shape. It does not measure body fat directly.

The Formula

ABSI = waist / (BMI^(2/3) x height^(1/2))

BMI = weight (kg) / height (m)^2

Waist and height are in meters, weight in kilograms

The formula comes from a 2012 study of US national survey data, where the authors found how waist size normally scales with height and weight and defined ABSI as your waist divided by that expected value¹.

How This Calculator Computes Your Result

Enter your height, weight and waist in metric or imperial units. The tool converts inches to meters and pounds to kilograms, then works out your BMI and your ABSI. ABSI is shown to 4 decimal places, such as 0.0786, because most adult values fall close to 0.08.

It also shows the average waist for adults of your height and weight in the original study, based on the study's overall average ABSI of 0.0808, and how far above or below it your waist is in percent¹. It does not give a z-score, which compares you with people of your own age and sex. That needs the study's full table of averages for every age, which we could not check line by line, and a score from an unchecked table could mislead you.

What Your Result Means

There is no official healthy or unhealthy ABSI cut-off². In research, ABSI is compared with people of the same age and sex, because average ABSI rises with age and is higher in men than in women after young adulthood¹. In the original study, each step of one standard deviation (the typical spread around the average) above average for age and sex was linked with a 33% higher death rate over about 5 years¹.

The same study split adults into five equal groups by ABSI within their age and sex. This is how death rates compared with the middle group¹:

So the risk signal sits mainly above average. If your waist is larger than the typical waist the calculator shows, your ABSI is above the study average.

How to Measure Correctly

ABSI was built on waist measurements from the US National Health and Nutrition Examination Survey (NHANES), so it works best if you measure the same way⁵.

• Find the top of your right hip bone at the side of your body. Place the tape just above it⁵.

• Keep the tape level all the way around, snug but not pressing into the skin⁵.

• Read it at the end of a normal breath out, without pulling your stomach in⁵.

• Measure on bare skin, take two readings, and use the average. A reading that is off by 2 to 3 cm can shift ABSI noticeably.

What ABSI Adds Beyond BMI

BMI cannot tell where weight is carried, and waist size rises with BMI, so the two overlap. ABSI removes the part of waist size that height and weight already explain. In a European study of 352,985 adults, ABSI was almost unrelated to BMI³.

In the original study of 14,105 US adults, ABSI predicted death in a simple straight-line model while BMI and waist size did not, and about 22% of the death risk in that population was linked to high ABSI¹. In the European study, people in the high-ABSI group had a 22% to 55% higher death rate than people in the low-ABSI group with the same BMI³. The authors concluded that a waist index should add to BMI, not replace it³.

What Later Studies Found

A 2018 review pooled 38 studies from 15 countries². Each one standard deviation rise in ABSI was linked with 55% higher risk of death from any cause, 21% higher risk of heart disease and stroke, 35% higher odds of type 2 diabetes and 13% higher odds of high blood pressure². ABSI beat BMI and waist size for predicting death, but it was weaker than them for predicting these conditions². The review also noted that ABSI values cluster tightly, which makes a clinical cut-off hard to set².

ABSI vs Body Roundness Index

The Body Roundness Index (BRI) also uses waist and height, but it treats the body as an ellipse to estimate total and visceral (deep belly) fat⁴. BRI goes up whenever your waist grows relative to your height, which usually happens as BMI goes up. ABSI is designed to stay flat as BMI changes, so it shows shape apart from size. For example, someone 160 cm tall, weighing 140 kg, with a 130 cm waist has a BMI of 54.7 and a waist-to-height ratio of 0.81, but an ABSI of 0.0713, below average. Their waist is large, but not large for their size. That is why ABSI is read alongside BMI, never instead of it³.