What this calculator does
BMI cannot tell where weight is carried, and waist circumference on its own is confounded by overall size. ABSI was designed to separate the two: it adjusts waist for both BMI and height, leaving the part of waist size that is not explained by being larger overall.
The result is a small decimal, which makes it hard to read in isolation. At a BMI of 24.5, a waist of 75 cm gives 0.0672 and a waist of 100 cm gives 0.0896, so the direction is clear even though the scale is unfamiliar.
The formula
Waist in metres is divided by BMI to the power of two thirds multiplied by the square root of height in metres. The exponents were fitted so the result is statistically independent of BMI and height.
| Term | Meaning |
|---|---|
| ABSI | A Body Shape Index: waist adjusted for BMI and height. |
| Central adiposity | Fat carried around the abdomen, which ABSI is designed to capture. |
| Independence from BMI | The fitted exponents mean ABSI carries information BMI does not. |
The inputs explained
| Field | What to enter |
|---|---|
| Waist circumference (cm) | Waist circumference in centimetres, measured at the level of the navel. |
| Height (cm) | Height in centimetres. |
| Weight (kg) | Weight in kilograms, used to compute BMI. |
When to use it
Looking beyond BMI
Two people with identical BMI can carry weight very differently, which ABSI reflects.
Tracking a change in shape
A falling ABSI at stable weight indicates waist reducing relative to overall size.
Understanding population research
ABSI appears in epidemiological studies of mortality risk and is worth being able to compute.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does waist size move the index?
The same height and weight at three waist measurements.
Questions
What ABSI value is high?
There is no single threshold. ABSI is normally interpreted against age and sex-specific population percentiles rather than a fixed cut-off, which is a real limitation for anyone calculating it on their own.
Why are the exponents so unusual?
They were fitted statistically so that the resulting index is uncorrelated with BMI and height. The two-thirds and one-half powers have no physiological meaning; they exist to make ABSI independent of the things it is meant to add to.
Is ABSI better than waist-to-height ratio?
Not clearly. Studies have found ABSI predicts mortality well in some populations, while waist-to-height ratio is simpler and performs comparably in others. Neither has displaced the other in practice.
Can I use this to assess my health?
Only as one crude indicator among many. It knows nothing about your blood pressure, blood sugar, fitness or family history, all of which matter more. Any health assessment belongs with a clinician.
For a fat percentage estimate from the same waist measurement, see the relative fat mass calculator. For the standard weight-for-height measure, see the BMI calculator.