How to use
- Choose cm / kg or ft·in / lb.
- Enter your height and weight.
- Read your BMI, its category and the healthy weight range for your height.
BMI categories (WHO, adults)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obesity class I |
| 35.0–39.9 | Obesity class II |
| 40 and above | Obesity class III |
How BMI is calculated
BMI = weight in kilograms ÷ (height in metres)². For example, 65 kg at 1.70 m gives 65 ÷ 2.89 = 22.5. In imperial units: 703 × weight in pounds ÷ (height in inches)².
Frequently asked questions
Is BMI accurate for everyone?
No. It doesn’t distinguish muscle from fat, so athletes may score high. It is a quick screening measure, not a diagnosis.
Does BMI work for children?
Not with these categories. Children and teenagers are assessed with BMI-for-age percentiles that depend on age and sex.
Why do some countries use different cut-offs?
Studies show higher health risks at lower BMI in some Asian populations, so Japan, for example, classes a BMI of 25 or more as obesity.