How to use the BMI calculator
- Choose cm and kg or feet and pounds.
- Enter your height and weight.
- Your BMI appears straight away, with its category, its place on the scale, and the healthy weight range for your height.
The formula
BMI = weight (kg) ÷ height (m)²
For someone 170 cm tall weighing 70 kg: 70 ÷ (1.70 × 1.70) = 24.2, which is in the healthy range. At that height, a healthy weight range is about 53.5 to 72.0 kg.
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity (class I) |
| 35.0 to 39.9 | Obesity (class II) |
| 40.0 and above | Obesity (class III) |
These are the World Health Organization categories for adults aged 18 and over.
What BMI can’t tell you
BMI is a quick screening number, not a diagnosis. It doesn’t measure body fat directly or show where fat is stored, and it doesn’t reflect muscle mass, age or overall fitness. Children and teenagers are assessed with growth charts instead.
If you have questions about your weight or health, talk to a doctor.