A Body Shape Index (ABSI) Calculator
A Body Shape Index (ABSI) combines waist circumference, height, and weight into a single number that captures body shape — how much of your size sits around your middle — independently of BMI. Introduced by Krakauer & Krakauer in 2012, higher ABSI tracked with higher mortality risk in the NHANES cohort even at the same BMI. Enter three measurements plus your age and sex to also get your z-score: where your ABSI sits relative to the US reference population of your age and sex.
The z-score reference covers adults 18–85
The population reference table is sex-specific (NHANES)
Measure at the navel, standing relaxed, at the end of a normal exhale
Enter your values above to see your results.
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How it works
The formula
ABSI = waist circumference ÷ (BMI^⅔ × √height), with waist and height in meters and BMI in kg/m² — this page converts inches and pounds for you. The exponents were chosen so that ABSI is statistically near-independent of BMI, height, and weight: it isolates body shape (how round the midsection is) from body size. That is the difference from BMI, which cannot tell where weight is carried.
What the z-score means
A raw ABSI number (typically ~0.07–0.09 in adults) means little on its own — the average shifts with age and differs by sex. The z-score fixes that: it expresses your ABSI as standard deviations above or below the mean of the US NHANES reference group of your age and sex (1999–2004 cohort, via the formula authors' published reference table). A z-score of 0 is exactly average; the bands above divide the population into fifths, matching how the original research reported risk.
Limitations — read this before your number
ABSI is a research-stage metric with no official clinical cut-offs, and the mortality associations come from observational cohorts (US NHANES, 1999–2004) — they describe population-level risk gradients, not individual predictions, and may transfer imperfectly to other populations. It is less informative during pregnancy and in very muscular builds. This is a screening signal, not a diagnosis: use it next to waist-to-height ratio, blood pressure, lipids, and glucose, and discuss concerns with a qualified practitioner.
Frequently asked questions
What is A Body Shape Index (ABSI)?
ABSI is a body-shape metric introduced by Nir Krakauer and Jesse Krakauer in 2012. It combines waist circumference with BMI and height so that the result reflects how much of your body size concentrates around your middle — statistically independent of how heavy or tall you are. In the NHANES cohort, higher ABSI predicted higher mortality risk even among people with the same BMI.
What is a good ABSI score — is there a cut-off?
There is no official cut-off. ABSI is interpreted relative to the reference population: your z-score shows where you sit among people of your age and sex, and the original study reported risk by fifths (quintiles) of that distribution. The highest fifth carried roughly double the mortality hazard of the middle fifth in NHANES — a risk gradient, not a pass/fail line.
How is ABSI different from BRI (Body Roundness Index)?
Both are tape-measure-era answers to BMI's blind spot — central fat. ABSI (2012) uses waist, height, and weight, and is built to be independent of BMI; BRI (2013) models the body as an ellipse from waist and height alone, no scale needed. They correlate strongly but are computed differently; our Body Roundness Index Calculator covers BRI.
Is this the same ABSI used for burn injuries?
No — same acronym, unrelated metric. The Abbreviated Burn Severity Index estimates survival after burn trauma from age, sex, and burn area. This page computes A Body Shape Index, the body-composition metric from waist, height, and weight.
Can I enter centimeters and kilograms?
This page takes inches and pounds and converts internally. To convert first: divide centimeters by 2.54 for inches, multiply kilograms by 2.205 for pounds. The underlying formula itself is defined in SI units, so the conversion is exact.
Is a high ABSI a diagnosis?
No. ABSI is a screening signal, not a diagnosis. The mortality associations come from population cohorts and describe averages, not individual outcomes. A higher z-score is a prompt to review the fuller picture — blood pressure, lipids, fasting glucose, symptoms — with a qualified practitioner.
Sources
- Krakauer NY, Krakauer JC. A new body shape index predicts mortality hazard independently of body mass index. PLoS One, 2012.
- Krakauer NY, Krakauer JC. Dynamic association of mortality hazard with body shape. PLoS One, 2014.
- Reference table: age- and sex-specific ABSI means and SDs, US NHANES 1999–2004, via the formula authors' open-source reference calculator (nirkrakauer.net, GPLv3).
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.