Australian BMI calculator

Body mass index (BMI) is a number calculated from your height and weight (kg ÷ m²) that screens whether your weight is in a healthy range for your height. Australian BMI categories follow the NHMRC clinical practice guidelines, which adopt the World Health Organization adult thresholds: under 18.5 (underweight), 18.5–24.9 (healthy weight), 25.0–29.9 (overweight), 30.0–34.9 (obese class I), 35.0–39.9 (obese class II), and 40 or above (obese class III). BMI is a screening tool, not a diagnosis.

The NHMRC defines the healthy adult BMI range as 18.5 to 24.9. Within this band, the average adult Australian has the lowest population-level risk of cardiovascular disease, type 2 diabetes, and obesity-related cancers. Individual risk also depends on waist circumference, blood pressure, lipids, fitness, family history, and ethnicity — your GP looks at the full picture, not just BMI.

No. BMI is a population-level screening tool, not a diagnostic test. It doesn't distinguish muscle from fat, so highly muscular adults (athletes, manual workers) can have a high BMI without excess body fat. It also doesn't apply to children (who use age-and-sex specific percentiles), pregnant or breastfeeding women, or older adults where natural changes in body composition shift the relationship between BMI and health risk. NHMRC also notes risk thresholds are lower for people of South or East Asian descent.

BMI compares weight to height, while waist circumference measures abdominal fat directly. The two are complementary, not interchangeable. Healthdirect Australia and the NHMRC both recommend GPs consider waist circumference alongside BMI because central (abdominal) fat carries a higher cardiovascular and type 2 diabetes risk than fat stored elsewhere. NHMRC adult thresholds flag increased risk above 94 cm in men and 80 cm in women, with substantially increased risk above 102 cm in men and 88 cm in women. Someone with a healthy BMI but a high waist circumference may still benefit from a GP review.

Yes — risk of type 2 diabetes and cardiovascular disease rises at lower BMI values for many people of South or East Asian descent. Public health bodies, including the NHMRC and the WHO, recommend GPs use lower thresholds for these populations: overweight risk from BMI 23 (rather than 25) and increased risk from BMI 27.5 (rather than 30). The calculator above shows the standard categories — talk to your GP for an individualised interpretation.

Standard adult BMI categories don't apply during pregnancy. Pregnancy weight gain depends on your pre-pregnancy BMI, with separate ranges set out in NHMRC and Royal Australian and New Zealand College of Obstetricians and Gynaecologists guidelines. Don't use this calculator to interpret pregnancy weight — speak to your GP or maternity care provider.

Not reliably. Muscle is denser than fat, so a heavily muscular adult can fall in the overweight or obese BMI range while having low body fat. If you train regularly with significant strength work, ask your GP about alternative measures such as waist circumference, waist-to-height ratio, or body composition (DEXA) before drawing conclusions from BMI alone.

A high BMI is a signal worth acting on, not a diagnosis. The NHMRC recommends a structured approach — lifestyle changes (diet quality, physical activity, sleep, alcohol), screening for related conditions (blood pressure, blood glucose, lipids), and where appropriate, GP-coordinated management plans or referrals. Bulk-billed telehealth makes the first conversation easy: a NewDoc GP can run baseline screening, set up a plan, and refer to allied health (dietitian, exercise physiologist) if helpful.

Yes. NewDoc offers bulk-billed telehealth GP consultations for eligible Medicare cardholders, including weight-related concerns. Where clinically appropriate, the GP can set up a Chronic Disease Management Plan or GP Management Plan, which gives access to subsidised allied health appointments under Medicare. There is no out-of-pocket cost for the consultation itself.

Yes. Medicare, the Department of Health, and most clinical guidelines use BMI as one of several entry criteria — for example, the Heart Health Check (MBS items 699/177) considers BMI alongside other cardiovascular risk factors. BMI also appears in NHMRC guidance for chronic disease management plans, and in eligibility for some specialist or surgical pathways. Your GP can advise on which criteria apply to you.

BMI = weight in kilograms divided by height in metres squared. For someone 1.70 m tall and 70 kg: BMI = 70 ÷ (1.70 × 1.70) = 24.2. For imperial units, the equivalent is BMI = (weight in pounds × 703) ÷ height in inches squared. The calculator above does this for you in either unit system.