What is BMI?
Body Mass Index (BMI) is a simple screening number that relates your weight to your height. It's calculated as your weight in kilograms divided by the square of your height in metres:
BMI = weight (kg) ÷ height (m)²
BMI categories (adults)
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obesity | 30 and above |
What BMI does — and doesn't — tell you
BMI is a quick, useful screen for populations, but it has real limits for individuals. It doesn't distinguish muscle from fat, so very muscular people can read as "overweight" while being lean. It also doesn't account for age, sex, or where body fat is stored.
Treat BMI as a starting point for a conversation — not a diagnosis. Waist circumference, body-fat percentage, and a doctor's assessment give a fuller picture.
This tool is for general information only and is not medical advice. Consult a healthcare professional about your individual health.