Calculate your ABSI
ABSI = waist / (BMI2/3 × height1/2), with waist and height in metres (Krakauer & Krakauer 2012).
Your ABSI
ABSI z-score (vs your age & sex)
How ABSI is calculated
From Krakauer & Krakauer (2012), PLoS ONE 7(7):e39504 — based on 14,105 US adults (NHANES 1999–2004).
Waist circumference and height in metres, BMI in kg/m². The exponents 2/3 and 1/2 come from an allometric regression of log waist on log height and log weight — they make ABSI nearly uncorrelated with height, weight and BMI, so it isolates shape from size.
- 252/3 = 8.5499
- √1.75 = 1.3229
- Denominator: 8.5499 × 1.3229 = 11.3104
- ABSI = 0.90 ÷ 11.3104 = 0.0796
ABSI z-score risk bands
Population bands used with the Krakauer materials (quintile-based). They describe a number’s position in the reference population — not a diagnosis.
| ABSI z-score | Band | What it means (educational) |
|---|---|---|
| below −0.868 | Very low | waist well below expected for your age, sex, height & weight |
| −0.868 to −0.272 | Low | waist below expected |
| −0.272 to +0.229 | Average | waist about as expected |
| +0.229 to +0.798 | High | waist above expected — more central body volume |
| above +0.798 | Very high | waist well above expected |
In the original cohort, mortality hazard rose progressively across these bands (top two quintiles significantly elevated vs the middle), while BMI and waist showed U-shaped risk (elevated at both extremes).
Reference population
Z-scores are computed against the smoothed age- and sex-specific ABSI means and standard deviations from Table S1 of Krakauer & Krakauer 2012: 14,105 non-pregnant adults aged 18+ from the US National Health and Nutrition Examination Survey (NHANES 1999–2004). Average ABSI rises steadily from midlife into old age and is higher in men than women after young adulthood. Because the reference is a US population measured in 1999–2004, treat results as a comparison against that group.
Study estimates: mortality hazard about 33% higher per standard deviation of ABSI (95% CI 20–48%); about 22% of population mortality hazard attributable to high ABSI vs ~15% each for BMI and waist circumference. Association held after adjusting for smoking, diabetes, blood pressure and cholesterol.
ABSI vs BMI vs waist-to-height
| Metric | What it captures | Limitation |
|---|---|---|
| BMI = weight/height² | overall body size | cannot distinguish muscle from fat, or where fat sits |
| Waist circumference | abdominal size | confounded by height and body mass |
| ABSI | waist relative to height & BMI — body shape | population indicator; needs age/sex reference |
| Waist-to-height | simple abdominal proportion (target often cited < 0.50) | does not adjust for overall body mass |
For a plain BMI number, see our BMI calculator.
Frequently asked questions
What is A Body Shape Index (ABSI)?
A Body Shape Index (ABSI) is a health-risk indicator developed by Krakauer and Krakauer in 2012 (PLoS ONE). It combines waist circumference, height and BMI into a single number that reflects body shape — specifically, whether your waist is larger than expected for your height and weight. In the original US population study, higher ABSI was associated with higher mortality hazard independently of BMI, which is why ABSI is designed to complement BMI, not replace it. This tool is educational only and cannot diagnose any condition.
How is ABSI calculated? What is the formula?
ABSI = WC / (BMI^(2/3) x height^(1/2)), where waist circumference (WC) and height are both in metres and BMI is in kg/m². Worked example: a person 175 cm tall with BMI 25 (about 76.6 kg) and a 90 cm waist. Step 1: 25^(2/3) = 8.5499. Step 2: sqrt(1.75) = 1.3229. Step 3: multiply, 8.5499 x 1.3229 = 11.3104. Step 4: 0.90 / 11.3104 = 0.0796. So ABSI = 0.0796.
What is a good ABSI score?
Most adults fall roughly between 0.07 and 0.09, but there is no single universal cutoff, because average ABSI rises with age and differs by sex. A raw score is best interpreted as a z-score against people of your age and sex: the calculator compares your ABSI with the NHANES 1999-2004 US reference population and reports how many standard deviations above or below average you are, plus a population risk band.
What does the ABSI z-score mean?
The z-score is (your ABSI - reference mean) / reference SD, using the age- and sex-specific smoothed means and standard deviations tabulated in the original Krakauer paper (Table S1, NHANES 1999-2004). A z-score of 0 means you match the reference average for your age and sex; +1 means one standard deviation above average; -1 means one standard deviation below. The calculator also converts it to an approximate percentile.
What are the ABSI risk classes?
ABSI z-scores are grouped into five population bands used with the Krakauer materials: below -0.868 = Very low; -0.868 to -0.272 = Low; -0.272 to +0.229 = Average; +0.229 to +0.798 = High; above +0.798 = Very high. These bands describe where your body shape sits relative to the reference population — they are statistical groupings, not medical diagnoses.
How is ABSI different from BMI?
BMI (weight / height²) measures overall body size but cannot tell where fat is stored — a muscular athlete and a person with central obesity can share the same BMI. ABSI is nearly uncorrelated with BMI by design: it isolates the waist component that BMI does not explain. That is why the two are complementary: BMI flags overall size, ABSI flags central concentration of body volume. This calculator shows both side by side.
Is ABSI better than waist circumference alone?
Waist circumference alone is confounded by height and overall body mass — a 100 cm waist means something different on a 200 cm frame than on a 160 cm frame. ABSI adjusts waist for height and BMI using allometric scaling (the 2/3 and 1/2 exponents come from regressing log waist on log height and log weight in the NHANES sample), so it isolates the shape component. Studies found ABSI adds mortality-prediction value even after adjusting for BMI.
What does the estimated relative mortality hazard mean?
The original study estimated that mortality hazard rises approximately exponentially with ABSI z-score, about 33% higher per standard deviation (95% CI: 20%-48%), i.e. a hazard ratio of roughly 1.33^z. The calculator shows this as an estimate with its confidence interval — for example 1.11x (95% CI 1.07-1.16). This is a population-model estimate from one US cohort study, not a prediction about any individual, and it does not account for smoking, blood pressure, cholesterol, diabetes or fitness.
Which reference population is used?
The z-score reference values are the smoothed age- and sex-specific ABSI means and standard deviations from Table S1 of Krakauer and Krakauer 2012, based on 14,105 non-pregnant adults aged 18+ from the US National Health and Nutrition Examination Survey (NHANES) 1999-2004. Because the reference is a US population from 1999-2004, results are most meaningful as a comparison against that group, not as universal cutoffs.
Can I lower my ABSI?
Mathematically, ABSI falls when waist circumference shrinks relative to height and weight — for example, losing abdominal fat while preserving muscle tends to improve it, while losing weight with an unchanged waist can actually raise it. In general, the habits linked to healthier waistlines are regular physical activity, a balanced diet, enough sleep and not smoking. This is general educational information, not personal medical advice — discuss any health goal with a qualified professional.
Is ABSI the same as ABI (ankle-brachial index)?
No — the names look alike but they measure completely different things. ABSI (A Body Shape Index) is computed from waist, height and weight and describes body shape. ABI (ankle-brachial index) is a blood-pressure-based screening test for peripheral artery disease, comparing ankle and arm pressures. If you meant the blood pressure test, see our ankle-brachial index (ABI) calculator instead.
Is this ABSI calculator a medical diagnosis?
No. This is an educational statistics tool: it computes a published index, compares it with a published reference population, and reports population-level risk bands. It cannot diagnose disease, predict your personal health outcome, or replace professional advice. Always discuss results — and any concern about weight, waist or health risk — with a qualified healthcare professional.