Calculate your A Body Shape Index (ABSI) from waist circumference, BMI, and height. ABSI provides a body-shape reference that has been studied alongside mortality risk.
The A Body Shape Index (ABSI) is an anthropometric measure developed by Nir and Jesse Krakauer in 2012 that scales waist circumference to BMI and height. It provides a body-shape reference that can be compared across people with different body sizes.
The formula normalizes waist circumference by BMI raised to the 2/3 power and height raised to the 1/2 power. The raw value can then be converted to a z-score using age- and sex-specific reference values. In cohort studies, higher ABSI values have been associated with higher mortality risk, but the number should be read as a reference marker rather than a diagnosis.
ABSI is useful as a companion to BMI because it highlights whether a waist measurement is larger or smaller than expected for a given body size.
ABSI captures a dimension of body shape that BMI misses: abdominal size relative to overall build. Two people with the same BMI and height can have very different waist circumferences, and ABSI helps compare that difference in a standardized way. It uses only three routinely measured values and can be paired with reference tables for context.
ABSI = WC / (BMI^(2/3) × Height^(1/2)) Where: • WC = Waist circumference in meters • BMI = Weight (kg) / Height (m)² • Height in meters ABSI z-score = (ABSI − ABSI_mean) / ABSI_sd where ABSI_mean and ABSI_sd are age- and sex-specific population reference values from NHANES data. Some cohort analyses reported roughly a 13% higher all-cause mortality hazard per standard-deviation increase in ABSI z-score.
Result: ABSI = 0.0822
BMI = 85 / 1.75² = 27.76. ABSI = 1.00 / (27.76^(2/3) × 1.75^(1/2)) = 1.00 / (9.20 × 1.323) = 1.00 / 12.17 = 0.0822. Comparing to the NHANES reference mean of ~0.0807 for a 45-year-old male with SD ~0.0036, the z-score is (0.0822 − 0.0807) / 0.0036 ≈ 0.42. That is a mildly above-average body-shape reference, not a diagnosis.
ABSI was developed by Nir Y. Krakauer and Jesse C. Krakauer and published in PLoS ONE in 2012. The researchers analyzed NHANES data (1999–2004) and follow-up mortality data to create an index where waist circumference is normalized by body size. The key insight was that the allometric scaling exponents of 2/3 for BMI and 1/2 for height reduced the dependence of waist circumference on overall body mass, isolating the abdominal shape component.
The raw ABSI value is difficult to interpret in isolation because the range of values (roughly 0.07–0.09) is narrow. Converting to a z-score using age- and sex-specific mean and standard deviation values from NHANES provides a standardized scale. A z-score of 0 represents the population average, +1 is one standard deviation above average, and −1 is one standard deviation below average.
Multiple prospective studies have found associations between ABSI and mortality beyond BMI and waist circumference alone. In a meta-analysis of cohort studies, an increase of one standard deviation in ABSI z-score was associated with a hazard ratio of approximately 1.13 for all-cause mortality. ABSI is therefore best viewed as an additional body-shape marker alongside BMI and waist circumference.
ABSI does not distinguish between visceral and subcutaneous abdominal fat — both contribute to waist circumference. Population-specific reference values may be needed for non-Western populations where body proportions and fat distribution patterns differ. Ongoing research is exploring dynamic ABSI tracking as a biomarker for the effectiveness of lifestyle interventions.
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This page calculates raw ABSI as waist circumference divided by BMI^(2/3) and height^(1/2), with waist entered in meters and BMI derived from the height and weight inputs. When age and sex are entered, it also shows a z-score using the reference mean and standard deviation stored in the calculator. The output is a comparison aid, not a diagnosis or a stand-alone mortality prediction.
ABSI is an anthropometric index developed by Krakauer & Krakauer (2012) that measures abdominal size relative to overall body size. It divides waist circumference by a power function of BMI and height, isolating the component of waist that is not explained by general body size.
BMI measures overall mass relative to height but cannot distinguish fat from muscle or detect where fat is located. ABSI specifically captures abdominal size relative to body size. Two people with BMI 28 can have very different ABSI values depending on their waist size.
ABSI values are small numbers, typically ranging from 0.07 to 0.09. Because absolute values are hard to interpret, ABSI is usually converted to a z-score using age- and sex-specific reference tables from NHANES. A z-score near 0 is average; above +1 is higher than average; below −1 is lower than average.
A high positive z-score (e.g., +1 or above) means your waist is larger than expected for your BMI and height. In cohort studies, higher ABSI z-scores have been associated with higher mortality hazard, but the value should still be interpreted as a reference marker rather than a diagnosis.
ABSI can be more informative than BMI for muscular individuals because BMI inflates with muscle mass while ABSI focuses on waist relative to body size. An athlete with a BMI of 30 but a normal waist would generally have a lower ABSI than expected for someone carrying more abdominal fat.
ABSI was originally validated in adults. While the formula can be applied to younger individuals, the NHANES-based z-score reference tables are primarily for adults aged 18+. Pediatric versions with age-appropriate references are still under research development.
ABSI has been associated with all-cause mortality, cardiovascular mortality, and type 2 diabetes in prospective cohort studies. It is a risk marker, not a diagnostic tool, and should be used alongside clinical evaluations.
Recalculating every 3–6 months is reasonable for tracking body composition trends. Since ABSI depends on waist circumference, BMI, and height, ensure all three are measured accurately each time.