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Free Australian BMI calculator using centimetres and kilograms. Learn what your BMI number means, see your healthy weight range, and get answers to common questions.
Enter your height in centimetres and weight in kilograms. Your BMI and category update instantly.
Heads‑up: BMI is a screening tool. It doesn’t directly measure body fat or account for muscle mass, bone density, age, sex, or ethnicity. For a more rounded view, consider waist circumference and a chat with a clinician.
BMI = weight (kg) ÷ [height (m)]². Adult categories follow widely used cut‑offs: underweight (<18.5), healthy (18.5–24.9), overweight (25–29.9), and obesity classes I–III (≥30). Ranges reference Australian and international guidance.
BMI (Body Mass Index) is a quick screening calculation that compares your weight to your height. It’s widely used in Australia and internationally to group adults into weight categories. Your BMI number can help indicate risk for some health conditions, but it doesn’t diagnose anything on its own.
Formula: BMI = weight (kg) ÷ [height (m)]². For example, if you weigh 70 kg and are 170 cm tall (1.70 m): BMI = 70 ÷ (1.70×1.70) = 24.2.
These are the commonly used adult cut‑offs:
| Category | BMI (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity class I | 30.0 – 34.9 |
| Obesity class II | 35.0 – 39.9 |
| Obesity class III | ≥ 40.0 |
Waist circumference complements BMI. Many Australian heart‑health resources flag increased risk above 94 cm for men and 80 cm for women. Consider discussing your numbers with a clinician.
Based on the healthy BMI band (18.5–24.9). Use this table as a guide and consider your personal context.
| Height (cm) | Healthy range (kg) |
|---|
For most adults, a BMI between 18.5 and 24.9 is considered the healthy range. Your personal targets may differ based on your health history, medications, and body composition.
BMI uses the same formula and cut‑offs for women and men. However, body fat distribution and health risks can differ, which is why waist measurements and clinical context matter.
BMI is a simple screening measure, not a diagnosis. It’s useful at a population level and as a starting point for individuals, but it doesn’t distinguish between muscle and fat or account for ethnicity, age, or bone density.
BMI = weight (kg) ÷ [height (m)]². Enter centimetres and kilograms above and the calculator handles the maths for you.
Overweight is 25.0–29.9. Obesity is ≥30 and is grouped into classes I (30.0–34.9), II (35.0–39.9) and III (≥40).
People with high muscle mass may register a higher BMI despite low body fat. In that case, waist measurement and clinical markers are more informative than BMI alone.
This tool is for adults (18+). Children and teens use age‑ and sex‑adjusted growth charts. Speak with a GP if you have questions about a young person’s growth.
Aim for gradual, sustainable changes: balanced nutrition, regular physical activity, sleep and stress management. If appropriate, a clinician can discuss medical options and safe targets for you.
Related: Same‑day telehealth
BMI isn’t used in the same way during pregnancy. Your antenatal team will advise on weight gain targets and care plans that are right for you.
Need tailored advice? You can speak with an AHPRA‑registered Partner Doctor from anywhere in Australia.
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