Health & nutrition Australia
BMI Calculator Australia
Body mass index compares your weight with your height. Australian health bodies use the WHO categories to describe it, and it is a screening number, not a diagnosis. This calculator works out your BMI, the category and the weight range that sits in the healthy band for your height.
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BMI categories below are for adults over 18.
Your BMI
—Category
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Healthy weight range for your height
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Difference from the healthy range
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Weight in kg
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Height in metres
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The working
Working with a different rate? Edit the rates this calculator uses
These are the figures we verified on 2026-10-26. Change them to work with a historic period, or with a new rate that has been announced but which we have not published yet.
WHO adult category
WHO adult category
WHO adult category
A screening number, not a diagnosis. BMI is a screening measure for adults. It does not account for muscle, age, ethnicity or where fat is carried, and it should not be used to diagnose. If you are concerned about your weight, speak to a GP or dietitian. This calculator does not apply to children or teenagers, whose healthy range depends on age and sex.
How do I calculate my BMI?
Divide your weight in kilograms by your height in metres squared. A person who weighs 75 kg and is 1.75 m tall has a BMI of 24.5, which is in the healthy range of 18.5 to 24.9. BMI does not measure body fat or where it sits, so waist size and a conversation with a GP give a fuller picture.
What the categories mean
The categories come from the World Health Organization and are used by the Australian Institute of Health and Welfare and the Department of Health. They describe population-level risk, with the risk of conditions such as type 2 diabetes and heart disease rising across the overweight and obese bands.
People of some ethnic backgrounds have a higher risk at a lower BMI, and some health authorities use lower thresholds for them. A GP can advise what applies to you.
Beyond BMI
Waist circumference, blood pressure, blood sugar and cholesterol say more about health than a single number. Waist measurement above 94 cm for men and 80 cm for women is commonly used to flag higher risk, though your doctor will interpret it.
For daily energy needs, use the kilojoules to calories calculator.
How this is calculated
The rule, step by step, so you can check any figure by hand.
BMI = weight in kg ÷ (height in m)²WHO adult categories: under 18.5 underweight; 18.5 to 24.9 healthy; 25 to 29.9 overweight; 30 and over obesehealthy weight range = 18.5 × height² to 24.9 × height²
BMI squares the height because weight rises roughly with the cube of height in a scaled body, and the square is a compromise that works in the middle of the range. It is crude: a muscular person can have a BMI in the overweight range with low body fat, and an older person can have a healthy BMI with little muscle.
Australian guidance notes that other measures, such as waist circumference, help assess health risk, and that the categories do not apply the same way to everyone. Treat BMI as one data point.
A worked example
A person who weighs 75 kg and is 175 cm tall.
- Height in metres squared3.0625
- BMI, 75 ÷ 3.062524.5
- CategoryHealthy (18.5 to 24.9)
- Healthy range for 175 cm56.7 to 76.3 kg
A BMI of 24.5, in the healthy range.
The healthy range is a band, not a target.
Children and teenagers
BMI for children and teenagers is read against growth charts by age and sex, not against the adult thresholds. If you are concerned about a child's weight, ask a GP or child health nurse.
Using the result
If your BMI is outside the healthy range, it is a prompt to check in with a health professional rather than a verdict. Many people in the overweight range are healthy, and some in the healthy range are not.
What this calculator does not do
- Adults over 18 only
- Does not measure body fat or where it is carried
- WHO categories; some groups have different thresholds
- A screening measure, not a diagnosis
Common questions
What is a healthy BMI in Australia?
18.5 to 24.9 for most adults, using the WHO categories.
How do I calculate BMI?
Weight in kilograms divided by height in metres squared.
Is BMI accurate?
It is a rough screening tool. It does not distinguish muscle from fat, so use it alongside other measures.
Does BMI apply to children?
No. Children are assessed against growth charts for their age and sex.
What should I do if my BMI is high?
Talk to a GP or dietitian. A change in diet, activity and sleep is often the first step.
Where these numbers come from
- Australian Institute of Health and Welfare — overweight and obesity How BMI categories are used to describe Australians' weight
- Healthdirect — body mass index A plain-English explanation of BMI and its limits
Rates last verified 2026-10-26 Every figure Australian Institute of Health and Welfare sets is re-checked against the source at least once a year, and again whenever a change is announced. Out of date? Tell us and we will fix it.
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