What BMI tells you
Body mass index (BMI) is a simple number that compares your weight with your height: weight in kilograms divided by height in metres squared. Health services use it as a quick screening tool to see whether weight might be a concern. It does not measure body fat directly and it is not a diagnosis.
This calculator works in metric (kg and cm) or imperial (pounds and inches), shows your BMI on a four-zone gauge from underweight to obese, and gives the weight range that falls in the healthy band for your height. Your numbers stay in your browser.
How to use it
- Choose metric or imperial units.
- Enter your height and weight.
- Read the BMI value, the category badge and the healthy weight range for your height.
BMI categories for adults
The commonly used World Health Organization ranges for adults are:
Below 18.5 Underweight
18.5 to 24.9 Healthy weight
25.0 to 29.9 Overweight
30.0 and above ObeseLimits of BMI
Treat the result as one input, not a verdict:
- BMI does not tell muscle from fat. Athletes can score high without excess fat.
- It does not show where fat is carried. Waist size and body shape also matter.
- Ranges differ for children and teenagers, who are assessed against growth charts for their age.
- Age, sex, ethnicity and health conditions can change what is healthy for a person.
Talk to a professional
This tool gives general information and is not medical advice. If your result worries you, or you are planning a major change in diet or exercise, speak to a doctor or a registered dietitian who can look at your whole health picture.
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