Body mass index (BMI) calculator
Enter your height and weight to find out your body mass index instantly. Your details are never sent anywhere.
BMI ranges
| BMI (kg/m²) | Classification |
|---|---|
| < 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (class I) |
| 35.0 – 39.9 | Obesity (class II) |
| ≥ 40.0 | Obesity (class III) |
World Health Organization (WHO) classification for adults. Formula: weight (kg) ÷ height² (m²)
Reading your result
- BMI is a simple screening measure of your weight relative to your height; it does not distinguish muscle from fat.
- It can be misleading for people with high muscle mass, during pregnancy and in older age.
- Children and teenagers are assessed with growth charts based on age and sex; this calculator is for ages 18 and over.
- The result is not a diagnosis. Talk to your doctor about decisions regarding your health.
Frequently asked questions about BMI
How is body mass index calculated?
Your weight in kilograms is divided by the square of your height in metres. For example, someone who is 1.70 m tall and weighs 65 kg has a BMI of 65 ÷ (1.70 × 1.70) ≈ 22.5.
What is a normal BMI?
According to the World Health Organization, a BMI between 18.5 and 24.9 is considered normal for adults. 25 to 29.9 is overweight, and 30 or above is the obesity range.
Is BMI always accurate?
No. BMI does not distinguish muscle from fat and can be misleading for people with high muscle mass, during pregnancy and in older age. It should be read together with measures such as waist circumference and a professional assessment.
Can it be used for children?
No. Under 18, growth charts based on age and sex are used. Ask your paediatrician about your child’s development.
Why don’t you ask for my age and sex?
For adults, BMI is calculated from height and weight only. The World Health Organization uses the same cut-off points for women and men and for all ages over 18. Age and sex matter under 18, where children and teenagers are assessed with growth charts.
Sources
The BMI ranges and the explanations on this page are based on the sources below.
Last reviewed:
- Obesity and overweight (fact sheet) (opens in a new tab) World Health Organization (WHO)
- Obesity: preventing and managing the global epidemic (Technical Report Series 894) (opens in a new tab) World Health Organization (WHO), 2000
- Şişmanlık (Obesity) (opens in a new tab) Ministry of Health of Türkiye, 2012 (in Turkish)
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