A Body Shape Index Calculator
Calculate your A Body Shape Index (ABSI) from waist circumference, height and weight. ABSI shows how much abdominal fat you carry relative to your overall body size, complementing BMI.
Calculate ABSI from Your Waist, Height and Weight
ABSI Formula
Where:
- \(WC\) — waist circumference in metres, measured at the navel
- \(h\) — height in metres
- \(W\) — weight in kilograms
- \(BMI\) — body mass index in kg/m²
The formula, proposed by Krakauer and Krakauer in 2012, expresses waist circumference relative to what would be expected for a person of your height and weight. Because height and weight are divided out, ABSI isolates the one thing BMI cannot see: where on the body the mass is concentrated.
ABSI – Calculation Example
{example}
Example: a person with a waist circumference of 90 cm, a height of 175 cm and a weight of 75 kg.
\[ BMI = \frac{75}{1.75^{2}} = 24.5 \,\mathrm{kg/m^2} \]
\[ \mathrm{ABSI} = \frac{0.90}{24.5^{2/3} \times 1.75^{1/2}} = \frac{0.90}{8.43 \times 1.3229} = 0.0807 \]
Result: ABSI = 0.0807, with a BMI of 24.5 kg/m². This ABSI is about average for adults, meaning the waist is proportionate to height and weight.
{/example}
How to Use the Calculator
- Measure your waist circumference at the navel while standing relaxed, with the tape parallel to the floor, and enter the value in the Waist circumference field (default: 90 cm).
- Choose the matching unit (cm or in) from the dropdown next to the waist field.
- Enter your height in the Height field and select cm, m or in.
- Enter your weight in the Weight field and select kg or lb.
- Read your results: the A Body Shape Index value, your Body Mass Index in kg/m², and the interpretation of what both numbers mean together.
What Is ABSI and Why Does It Matter?
A Body Shape Index (ABSI) is a measure of body shape developed to address a well-known weakness of BMI. BMI only compares total weight to height, so it cannot distinguish a muscular person from someone carrying the same weight as visceral fat around the abdomen. Two people with identical height, weight and BMI can have very different health risks depending on where their mass is distributed.
ABSI solves this by relating waist circumference to height and weight simultaneously. It is constructed so that it does not simply rise with body size: a larger waist than expected for a given height and weight pushes ABSI up, while a slim waist for the same frame pushes it down. In this way ABSI behaves like a shape indicator rather than a size indicator, and it is largely independent of BMI.
In the original research and subsequent studies, high ABSI values were associated with increased mortality risk — even among people whose BMI fell in the normal range. This makes ABSI a useful complementary check: if your BMI looks fine but your ABSI is high, the excess fat may be concentrated around the waist, a pattern linked to metabolic and cardiovascular problems.
For most adults, ABSI values cluster roughly between 0.075 and 0.081. Values below about 0.075 suggest a relatively small waist for your frame (favourable), while values above roughly 0.087 indicate a waist disproportionately large for your height and weight. Keep in mind that these are population-level tendencies, not personal diagnoses.
Measuring Your Waist Correctly
Because waist circumference is the only input that reflects body shape, measurement accuracy matters more for ABSI than for BMI:
- Stand relaxed, feet together, and breathe out normally before reading the tape.
- Place the tape horizontally at the level of the navel (some protocols use the midpoint between the lowest rib and the top of the hip bone — be consistent between measurements).
- Keep the tape snug but not compressing the skin, and take the measurement two or three times, using the average.
Assumptions and Limitations
The calculator converts all inputs to metric units internally, so you can enter cm, inches, metres, kilograms or pounds without worrying about conversions. Results assume the standard Krakauer and Krakauer formula, which was derived and validated on adult populations.
A few things to keep in mind when interpreting your result:
- ABSI is designed for adults. Its reference ranges do not apply to children, teenagers, or pregnant women.
- Population averages vary. Typical ABSI values differ somewhat by age, sex and ethnicity, so the interpretation bands used here are broad guides rather than precise thresholds.
- One measurement is a snapshot. Tracking how your ABSI changes over time — for example while losing weight or training — is more informative than a single number.
- ABSI does not replace medical assessment. A high value is a signal to look deeper, not a diagnosis. Consult a healthcare professional if your result concerns you.
To build a fuller picture of your body composition and health, you can pair ABSI with the Waist to Hip Ratio Calculator, which assesses fat distribution from another angle, or the Shoulder to Waist Ratio Calculator. If you are planning changes to your diet, our Daily Protein Intake Calculator and Katch-McArdle BMR Calculator can help you estimate your energy and protein needs.
Frequently Asked Questions
How do I calculate ABSI by hand?
First compute your BMI: \( BMI = \frac{W}{h^2} \) with weight in kilograms and height in metres. Then divide your waist circumference in metres by \( BMI^{2/3} \times h^{1/2} \). For example, with a 90 cm waist, 175 cm height and 75 kg weight: \( BMI = 24.5 \), so \( ABSI = \frac{0.90}{24.5^{2/3} \times \sqrt{1.75}} \approx 0.0807 \). Double-check that all lengths are converted to metres before calculating.
What is a normal or good ABSI value?
For most adults, ABSI values fall roughly between 0.075 and 0.081, which counts as average. Below about 0.075 means your waist is relatively small for your frame — generally favourable. Above roughly 0.087 suggests a waist disproportionately large for your height and weight, a pattern linked to higher mortality risk in studies. Typical values also drift slightly with age, sex and ethnicity, so treat these bands as broad guides rather than strict cut-offs.
Why does ABSI use waist circumference in metres instead of centimetres?
The Krakauer and Krakauer formula is defined with SI units: waist circumference and height in metres, weight in kilograms. If you plug in centimetres, the result will be off by a factor of 100. If you measured in inches or pounds, convert first — 1 inch = 0.0254 m and 1 lb = 0.4536 kg. The calculator handles all of these conversions automatically, so you can enter any supported unit directly.
Can ABSI be high when BMI is normal?
Yes, and this is exactly the scenario ABSI was designed to catch. Because the formula divides out height and weight, ABSI only reflects whether your waist is larger or smaller than expected for your body size. Someone with a 'healthy' BMI of 22 can still have a high ABSI if fat is concentrated around the abdomen — a pattern of visceral fat associated with metabolic and cardiovascular risk that BMI completely misses.
What is the difference between ABSI and BMI?
BMI is a size indicator: it only compares total weight to height, so it cannot tell muscle from fat or show where fat sits. ABSI is a shape indicator: it compares your waist circumference to what is statistically expected for your height and weight, isolating fat distribution. They answer different questions and are largely independent of each other, which is why researchers and clinicians increasingly use them together.
Does ABSI work for children, teenagers or pregnant women?
No. The formula and its reference ranges were derived and validated on adult populations, so the interpretation bands do not transfer to children, teenagers or pregnant women, whose body proportions change naturally during growth or pregnancy. For younger people, waist-to-height ratio or age- and sex-specific growth charts are more appropriate tools. If you have concerns about a young person's body composition, consult a paediatric healthcare professional.
What are common mistakes when measuring waist for ABSI?
The most frequent errors are measuring over clothing, pulling the tape too tight, or reading it after a deep inhalation. Stand relaxed with feet together, place the tape horizontally at the navel, exhale normally, and keep the tape snug without compressing the skin. Take the measurement two or three times and average the readings. Also measure at the same body level each time — switching between the navel and the midpoint between rib and hip will make your ABSI values hard to compare over time.