Adelaide Bariatric Centre

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Calculate Your BMI

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BMI Calculator

There are no perfect measures of overweight and obesity. Body Mass Index (BMI), which is calculated by dividing weight in kilograms by height in metres squared, is used most often – particularly in assessing overweight and obesity at the population level. 

At the individual level however, BMI does have some limitations in that it can be influenced by age, gender and ethnicity. Also, BMI does not distinguish fat mass from lean mass, nor does it necessarily reflect body-fat distribution.

For example, a woman 1.67m in height and weighing 65kg would have a BMI of 23.3, which falls within the healthy weight range. However, this may not be not an accurate predictor of the proportion of body fat to lean mass or fat distribution, particularly in older people or muscular individuals such as athletes, because of the differences in proportions of fat mass to lean mass and distribution of body fat.

The BMI cut-off points are based on associations between chronic disease and mortality and have been adopted for use internationally by the World Health Organisation (WHO).


BMI (kg/m2)

Risk of co-morbidities
(Health Consequences)

Underweight: <18.50 Low (but possibly increased risk of other clinical problems)
Normal range: 
(Healthy Weight)
18.50 - 24.99 Average
Overweight: >25.00
Pre-obese: 25.00 - 29.99 Increased
Obese Class 1: 30.00 - 34.99 Moderate
Obese Class 2: 35.00 - 39.99 Severe
Obese Class 3: >40.00 Very severe