BMI Calculator Australia
Calculate body mass index from height and weight, with a broad adult category and the weights corresponding to BMI 18.5 and 24.9 at that height.
What your BMI result means
For adults, BMI 18.5–24.9 is the standard healthy-weight reference range, 25–29.9 is overweight and 30 or above is obese. These are screening categories, not a diagnosis, and can misrepresent muscular builds or individual health risk.
On this page
What this calculator estimates
Calculate body mass index from height and weight, with a broad adult category and the weights corresponding to BMI 18.5 and 24.9 at that height. BMI is a screening measure; it does not directly measure body fat.
Inputs and calculation method
Enter height in centimetres and weight in kilograms. The calculator converts height to metres, divides weight by height squared and assigns a category using the unrounded BMI.
Formula and units
BMI = weight in kg ÷ (height in cm ÷ 100)². Reference weight = BMI boundary × height in metres². The main BMI and the reference weights are displayed to one decimal place.
How to use it
- Measure height without shoes and enter centimetres.
- Enter body weight in kilograms.
- Calculate and read the category together with the numerical BMI.
- Use the two weight values as BMI reference boundaries, not a personal weight-loss prescription.
Worked example
At 165 cm and 70 kg, BMI is 70 ÷ 1.65² = 25.7 after rounding. The calculator labels this “Above healthy range”. The weights corresponding to BMI 18.5 and 24.9 at this height are 50.4 kg and 67.8 kg.
How to read the result
The page uses boundaries below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above. Category wording is a broad reference. Muscle, pregnancy, age, ethnicity and clinical context can change how a health professional interprets BMI.
Common mistakes
- Entering metres such as 1.65 into the centimetre field.
- Reading BMI as body-fat percentage.
- Using adult categories for a child or teenager.
Method limitations
BMI cannot distinguish muscle, bone and fat or describe fat distribution. A category cannot establish an individual’s health or set an appropriate goal without other information.
Sources and method references
Supporting guides for this calculator
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BMI Calculator Australia FAQs
Is BMI a body-fat measurement?
No. It compares total mass with height squared and does not separate fat from lean tissue.
Why is the reference range different for different heights?
The weights are calculated from BMI 18.5 and 24.9 multiplied by height squared.
Can children use these categories?
This page uses broad adult categories. Children and teenagers require age- and sex-specific growth assessment.
Using the estimate
Read BMI alongside other relevant measurements and personal context. The calculation is straightforward; its health interpretation is more limited.