This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Why waist size adds to BMI
BMI tells you how heavy you are for your height, but not where the weight sits. Fat stored deep in the abdomen is the type most strongly linked to diabetes, heart disease and early death. A Body Shape Index (ABSI) and the conicity index both use waist circumference to capture that abdominal fat, independently of BMI.
The formulas
- ABSI = waist (m) ÷ (BMI^(2/3) × height (m)^(1/2))
- Conicity index = waist (m) ÷ (0.109 × √(weight (kg) ÷ height (m)))
ABSI was published in 2012 by Nir and Jesse Krakauer, who scaled waist circumference so that it is statistically independent of height, weight and BMI. The conicity index (Valdez, 1991) compares the body to a double cone: a value of 1.0 means a perfect cylinder, higher values mean more fat around the middle.
Example
A man 5 ft 9 in tall (1.75 m) weighing 180 lb (81.6 kg) with a 38 in (96.5 cm) waist has a BMI of 26.6, an ABSI of 0.0819, a conicity index of 1.30 and a waist-to-height ratio of 0.55.
Reading the results
| Indicator | Usual threshold |
|---|---|
| Conicity index, men | above about 1.25 |
| Conicity index, women | above about 1.18 |
| Waist-to-height ratio | 0.5 or more |
ABSI values are small numbers, typically 0.075 to 0.085 in adults. They are interpreted as a z-score against age- and sex-specific reference tables from the US NHANES survey: a z-score above about 0.8 is linked to a markedly higher risk of death in follow-up studies. Because ABSI rises naturally with age, compare a raw value only with people of your age and sex.
Limits
- Waist measurement must be standardized: at the navel or midway between the lowest rib and the top of the hip bone, after breathing out, the tape horizontal.
- These indices predict risk at the population level; they do not diagnose disease.
- The cut-offs come mainly from adult populations; they do not apply to children or pregnant women.
The simplest of all, the waist-to-height ratio, works well in practice: keep your waist under half your height.