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ABSI Calculator

Calculate your A Body Shape Index (ABSI), a measure that evaluates waist circumference relative to your height and BMI. Your ABSI z-score also compares your result with an age- and sex-specific population reference.

1

Your age

years
Your age is used to select the appropriate population reference for the ABSI z-score.
2

Sex

Sex is used to select the appropriate age-specific population reference.
3

Your weight

lb
Enter your current body weight. The calculator converts imperial values to metric for the formula.
4

Your height

ft
Enter your height in decimal feet, for example 5.75 ft. You can switch to cm below.
5

Your waist circumference

in
Measure your waist consistently at the same anatomical location and under similar conditions each time.

Measurement units

The calculator converts all measurements to the metric units required by the ABSI formula.

Your estimated ABSI:

0.00000

Your ABSI is calculated from your waist circumference, height and weight.

Your ABSI result

0.00000
ABSI
0.00
z-score
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This result is an informational estimate for educational purposes only and is not medical advice. ABSI is a population-based statistical measure and should not be used by itself to diagnose a medical condition or determine an individual's health status.
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How does the ABSI Calculator work?

The ABSI Calculator calculates your A Body Shape Index by relating waist circumference to your BMI and height. The method was developed to describe waist size relative to overall body size rather than simply using waist circumference or BMI alone. The calculator also produces an ABSI z-score by comparing the result with an age- and sex-specific population reference.

Term What does it mean? In the calculation Why does it matter?
Body weight Your current body mass, entered in pounds or kilograms. BMI calculation Body weight is one of the inputs used to calculate BMI.
Height Your standing height, converted to metres for the formula. BMI + ABSI Height helps normalize waist circumference relative to overall body size.
Waist circumference The circumference around your waist measured consistently at the same location. Main ABSI input ABSI specifically incorporates waist circumference to describe body shape.
BMI Body mass relative to height. Weight ÷ height² BMI is used to normalize waist circumference for overall body size.
ABSI A Body Shape Index, describing waist circumference relative to BMI and height. WC ÷ (BMI^(2/3) × height^(1/2)) It focuses on the waist component of body shape rather than body mass alone.
ABSI z-score The distance between your ABSI and the reference average expressed in standard deviations. (ABSI − mean) ÷ SD It puts the raw ABSI value into an age- and sex-specific population context.
Population reference The average ABSI and standard deviation for the relevant age and sex group. NHANES-derived reference ABSI varies with age and sex, so a population reference gives the raw value additional context.

1. Calculate BMI

The calculator first determines BMI from body weight and height. Weight is divided by height squared, using kilograms and metres for the underlying calculation.

2. Calculate ABSI

Waist circumference is then divided by BMI raised to the two-thirds power multiplied by the square root of height. This is the ABSI formulation developed by Krakauer and Krakauer.

3. Calculate the z-score

The raw ABSI is compared with an age- and sex-specific population reference. The resulting z-score tells you how far the ABSI is above or below that reference average in standard-deviation units.

1. BMI:
BMI = body weight ÷ height²

2. ABSI:
ABSI = waist circumference ÷ (BMI^(2/3) × height^(1/2))

3. ABSI z-score:
z = (ABSI − age/sex reference mean) ÷ reference standard deviation

4. ABSI z-score statistical ranges:
Very low: z < −0.868
Low: −0.868 ≤ z < −0.272
Average: −0.272 ≤ z ≤ 0.229
High: 0.229 < z ≤ 0.798
Very high: z > 0.798

ABSI is a statistical body-shape measure. A higher or lower z-score does not by itself indicate a disease or provide an individual medical diagnosis. The reference values are based on published ABSI norms derived from NHANES 1999–2004 data. For tracking changes over time, use consistent measurement locations and conditions because small differences in waist, weight or height can affect the result.

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Fitness Calculators
ABSI Calculator

ABSI Calculator estimates your A Body Shape Index using waist circumference, height and BMI. It also calculates an ABSI z-score to show how your result compares with an age- and sex-specific population reference. ABSI focuses on waist size relative to overall body size, providing information that BMI alone does not capture. Use the result as an informational body-shape and tracking measure rather than as a medical diagnosis.

Medical Disclaimer: The calculator results and information provided in this article are for educational and informational purposes only and do not constitute medical, health, or professional advice. Always consult with a qualified healthcare provider before making any decisions related to your health, diet, or fitness goals. Individual results may vary, and this tool should not be used to diagnose or treat any medical condition.

What is ABSI?

ABSI, or A Body Shape Index, is a body-shape measurement that evaluates waist circumference relative to height and BMI. It was developed to separate the waist component of body shape from overall body size. This means ABSI provides a different type of information from BMI, which primarily relates body weight to height.

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How is ABSI calculated?

ABSI is calculated using waist circumference, BMI and height. BMI is first calculated from body weight and height, and the resulting value is then used to normalize waist circumference. The final ABSI formula is waist circumference divided by BMI raised to the two-thirds power and height raised to the one-half power.

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What is the difference between ABSI and BMI?

BMI describes body mass relative to height but does not directly account for where that mass is distributed. ABSI specifically incorporates waist circumference and therefore describes a different aspect of body shape. The two measurements can be used alongside one another because they answer different questions.

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What is an ABSI z-score?

An ABSI z-score places your raw ABSI value into an age- and sex-specific population context. A z-score close to zero means your ABSI is close to the reference average, while a positive score indicates a value above that average. A negative score indicates that the ABSI is below the reference average.

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How should I measure my waist for ABSI?

Consistency is one of the most important parts of using ABSI for tracking. Use a non-stretch measuring tape and measure at the same anatomical location each time under similar conditions. Changes in tape placement, tension, clothing and breathing can all affect the waist measurement and therefore the calculated ABSI.

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Can ABSI help track fitness progress?

ABSI can be used as an additional body-shape metric alongside body weight, BMI and waist circumference. Over time, looking at several measurements together can provide more context than relying on a single number. ABSI is not a body-fat percentage measurement, so it should not be used as a replacement for direct body-composition measurements.

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