Guides
How this BMI calculator works
A short and checkable description of what happens when you type your numbers.
Short answer
The page converts your height to meters and your weight to kilograms, applies BMI = kg / m squared, rounds to one decimal and picks the WHO adult category for that rounded value. It all runs in your browser and nothing is sent.
Steps
- Feet and inches are converted to centimeters with 2.54 cm per inch, and pounds to kilograms with 0.45359237 kg per pound.
- BMI = weight (kg) / (height in meters x height in meters).
- The result is rounded to one decimal place for display.
- The category is chosen from the rounded value, so the label always matches the number you see: below 18.5, 18.5 to 24.9, 25 to 29.9, 30 to 34.9, 35 to 39.9, and 40 or more.
- The healthy weight range is 18.5 and 24.9 multiplied by height in meters squared.
Accepted values
Heights from 100 to 250 cm and weights from 20 to 500 kg are accepted. Decimal commas are understood. Values outside the range give a message instead of a result.
Privacy
- Your height and weight are not sent to a server and are not stored.
- The only thing remembered in your browser is whether you chose metric or imperial.
- Analytics, if you accept it, counts page visits and never receives your numbers.
The result is a screening number, not medical advice or a diagnosis.
Frequently asked questions
Why does the page not ask for age or sex?
The WHO adult categories are the same for men and women and do not depend on age within adulthood, so the calculation does not need them. They matter for interpreting the result, which is why a doctor should do that.