BMI calculator
Body mass index and the healthy weight range for your height.
About this calculator
BMI compares weight with height and is widely used to screen adults for weight-related health risks. The usual adult bands are under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight and 30 or above obesity.
BMI does not measure body fat directly, so it can mislead for muscular people, older adults and some ethnic groups. It is not designed for children. A clinician can tell you what your result means for you.
How it works
BMI is weight in kilograms divided by height in metres squared. Bands follow the WHO adult categories.
Worked example
- Units: Metric
- Height: 170 cm
- Weight: 70 kg
Your BMI: 24.2 (Healthy weight)
The story behind it
Where the idea came from: Adolphe Quetelet, Belgian mathematician, 1830s.
BMI began with Adolphe Quetelet, who was looking for patterns in the measurements of whole populations. It was known as the Quetelet index for over a century, until the American researcher Ancel Keys named it the body mass index in a 1972 study. It was designed to describe groups rather than diagnose individuals, which is why this page explains its limits.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, not medical advice.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
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