BMI Calculator
🇦🇺 Australia version
Australian health advice uses kilograms and centimetres, and the Department of Health reads BMI against WHO cut-offs from Underweight to Obesity class 3. This page opens in metric, shows the category with the weight range for your height, and repeats the Department's note that the healthy range is generally lower for people of Asian background. Ask your GP what the figure means for you.
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Categories: Department of Health adult categories (WHO cut-offs), Australian Government Department of Health: BMI and waist measurement.
The healthy range is generally lower for people of Asian background and higher for people of Polynesian background. No numbers are given.
Adult categories do not apply under 18; children are assessed on growth charts. BMI is also less accurate for teenagers.
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Australia rules and figures
- The Department of Health applies WHO cut-offs to adults, with Healthy weight at 18.5 to 24.9 and Overweight from 25. This page divides Obesity into three classes beginning at 30, 35 and 40.
- The Department says the healthy BMI range is generally lower for people of Asian background and higher for people of Polynesian background, without giving numbers.
- Adult categories do not apply under 18. Children are assessed on growth charts, and the Department notes BMI is also less accurate for teenagers.
- Kilograms and centimetres are the default units on the Australian page, so 170 cm and 70 kg are filled in when it opens.
Sources: Australian Government Department of Health: BMI and waist measurement (checked 2026-11-08)
How the BMI calculator works
Height in centimetres is turned into metres and squared, weight in kilograms is divided by it, and the answer is matched to the Department of Health band.
BMI = kg ÷ m². Department of Health bands run Underweight (under 18.5), Healthy weight (18.5 up to 25), Overweight (25 up to 30), then Obesity class 1, 2 and 3 starting at 30, 35 and 40
- Both boxes start in metric, filled with 170 cm and 70 kg. Choose ft, lb or st from the unit boxes and the page converts for you, and remembers that pick.
- The weight range under the result is 18.5 × height² up to 24.9 × height², so 160 cm gives 47.4 to 63.7 kg.
- The Department says the healthy range is generally lower for people of Asian background and higher for people of Polynesian background, and gives no numbers. The page therefore has no switch for it and shows the note instead.
- Adult categories do not apply under 18, and the Department adds that BMI is less accurate for teenagers.
How to use the BMI calculator
- Check the units are metric. The page starts on cm and kg. If your scales show pounds or stones, change the unit box beside Weight before typing.
- Type your measurements. Enter height in centimetres and weight in kilograms. The BMI and category update as you type.
- Compare the three methods. Standard BMI is what the Department's bands are written for. Age-Adjusted BMI and BMI Prime are extra views shown in the comparison list.
- Add a waist measurement. Waist in centimetres gives a waist-to-height ratio on the Body Composition tab. The Department pairs BMI with waist size.
- Save or copy it. Use Save Entry to keep a dated reading in this browser, or Copy to paste the result elsewhere.
Example: 160 cm and 78 kg compared with 170 cm and 70 kg
A person of 160 cm and 78 kg gets 30.5, Obesity class 1, with 47.4 to 63.7 kg as the healthy range. The opening values of 170 cm and 70 kg give 24.2, Healthy weight, a range of 53.5 to 72 kg and a BMI Prime of 0.97.
When to use the BMI calculator
- Checking a result from the scales. Enter the kilograms from a bathroom scale to see where the number falls in the Department of Health bands.
- Finding a weight band for your height. Read the Healthy Weight Range to see the kilogram limits of the healthy category at your height.
- Logging progress between appointments. Save an entry each time you measure, then compare the starting and current BMI on the tracking tab.
What the BMI calculator does not do
- BMI cannot tell muscle from fat, so a very muscular adult can be placed in a higher category.
- The Department gives no numbers for Asian or Polynesian backgrounds, so this page cannot adjust the cut-offs for them.
- Age-Adjusted BMI is the page's own add-on: from 65 it moves the lines to 23, 28 and 33, away from the Department's bands.
- It screens only. Your GP can interpret a BMI with waist size, blood pressure and history.
When something else is a better fit
- When you want a body fat estimate from neck and waist tape measurements, use the Body Fat Calculator.
- When you want a set of target weights for your height, use the Ideal Weight Calculator.
- When you are worried about your weight or a recent change, use a GP, who can look at more than height and weight.
Questions about the BMI calculator
What BMI is classed as healthy in Australia?
The Department of Health uses 18.5 to 24.9 for adults. Anything lower is Underweight, and from 25 upward the labels move through Overweight to Obesity, which this page splits into classes at 35 and 40.
Does the healthy range change with background?
The Department says it is generally lower for people of Asian background and higher for people of Polynesian background, but it gives no figures. This page applies the standard bands and shows that note under the result.
Why does my teenager get a result but no advice?
The calculator will compute any height and weight, but the adult categories do not apply under 18. The Department says children are assessed on growth charts and BMI is less accurate for teenagers, so ask a GP.
How is the healthy weight range worked out?
It is 18.5 times height in metres squared at the low end and 24.9 times that at the high end. For 170 cm, 1.70 squared is 2.89, giving 53.5 to 72 kg.