BMI calculator
Enter height and weight to calculate your body mass index for adults, with the World Health Organization (WHO) categories.
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🔒 Runs entirely in your browser – nothing you enter is uploaded or stored.
How to use it
- Choose metric or imperial units.
- Enter height and weight.
- Read the BMI, its WHO category and the weight range for a BMI of 18.5–24.9 at your height.
Last checked: October 2026 · Based on: WHO classification. Found a mistake? Use the form below – we fix confirmed errors and update the date.
Frequently asked questions
How is BMI calculated?
Weight in kilograms divided by height in metres squared: BMI = kg ÷ m².
What are the WHO categories?
Below 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight (pre-obesity), 30–34.9 obesity class I, 35–39.9 class II, 40 or more class III.
Is BMI accurate for everyone?
No. Athletes with lots of muscle, older adults and some ethnic groups may be misclassified. It is not used for children and teenagers in this form.