How to calculate your BMI
- Choose metric (centimeters and kilograms) or imperial units (feet, inches and pounds).
- Enter your height and weight. Your BMI and weight category appear immediately, with a marker on the scale.
- Below the scale you can see the healthy weight range for your height.
BMI formula
Body Mass Index is your weight divided by your height squared: BMI = weight (kg) ÷ height (m)². In imperial units: BMI = 703 × weight (lb) ÷ height (in)². For example, a person 1.70 m tall weighing 65 kg has a BMI of 65 ÷ 1.70² = 22.5.
BMI categories for adults
| Below 18.5 | Underweight |
|---|---|
| 18.5 – 24.9 | Healthy weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity class 1 |
| 35 – 39.9 | Obesity class 2 |
| 40 and above | Obesity class 3 |
These are the World Health Organization categories for adults aged 20 and over. Some countries in Asia use lower cut-offs, for example 23 for overweight, because health risks rise at lower BMI levels in those populations.
Limitations of BMI
BMI is a quick screening number, not a diagnosis. It does not tell muscle from fat, so athletes may score as overweight, and it does not show where fat is stored. It is not meant for children, teenagers or pregnant women. Talk to a doctor about your weight and health.