ABSI Calculator: A Body Shape Index, Z-Score and Mortality Risk Group

How it works

ABSI = WC ÷ (BMI^(2/3) × height^(1/2)), with waist circumference WC and height in meters and BMI in kg/m² · equivalently ABSI = WC × weight^(−2/3) × height^(5/6) · z = (ABSI − mean ABSI for your age and sex) ÷ SD · risk groups by z: under −0.868 very low, −0.868 to −0.272 low, −0.272 to +0.229 average, +0.229 to +0.798 high, over +0.798 very high

A Body Shape Index (ABSI) was introduced by Nir and Jesse Krakauer in 2012 to answer a weakness of BMI: two people with the same BMI can carry their weight very differently. ABSI divides your waist by the waist that would be expected for your height and weight, using the way waist size grows with BMI and height across the US population. Because of this, ABSI is almost independent of BMI and height, and a high value points to a more central (abdominal) build. Typical adult values are about 0.077 to 0.088, so the raw number is hard to read on its own. That is why the calculator compares it with the smoothed average and standard deviation for your exact age and sex from the authors’ NHANES 1999–2004 reference table and gives a z-score. In the original study of more than 14,000 US adults, death rates rose as ABSI z rose: the fourth and fifth fifths of the population had 1.46 and 1.93 times the hazard of the middle fifth, while the lower two groups were close to average. The calculator shows your risk group, the relative hazard of that group, your percentile and, in a table, the waist sizes that would place you in each group at your current height and weight, so you can see how much a smaller waist would move you. Waist-to-height ratio and the body roundness index also use waist and height, but they are not adjusted for BMI, age or sex; ABSI uses its own formula and reference tables. ABSI is a population research measure, not a diagnosis.

Worked example

A 45-year-old man is 70 in (1.778 m) tall, weighs 190 lb (86.18 kg) and has a 40 in (1.016 m) waist. BMI = 86.18 ÷ 1.778² = 27.26. ABSI = 1.016 ÷ (27.26^(2/3) × √1.778) = 1.016 ÷ (9.058 × 1.3334) = 0.08412. The reference for men aged 45 is 0.08165 with an SD of 0.00368, so z = (0.08412 − 0.08165) ÷ 0.00368 = +0.67, which is in the high group (+0.229 to +0.798, relative hazard 1.46) and around the 75th percentile. At his height and weight, a waist of 38.8 in would give an average ABSI.

Sources: Krakauer NY, Krakauer JC (2012). A new body shape index predicts mortality hazard independently of body mass index. PLOS ONE · MyTecBits: ABSI calculator (Krakauer smoothed mean and SD table by age and sex) · Wikipedia: Body shape index (z-score risk groups) · CCNY: New obesity measure predicts early death better than BMI

Frequently asked questions