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UnderweightNormalOverweightObese
How BMI is calculated
Body Mass Index is your weight divided by the square of your height, giving a single number used as a rough population-level screening measure, not a diagnosis of any individual's health.
BMI = weight (kg) / height (m)²
Standard BMI categories (WHO)
- Below 18.5. Underweight
- 18.5 – 24.9. Normal weight
- 25.0 – 29.9. Overweight
- 30.0 and above. Obese
BMI doesn't account for muscle mass, bone density, age, or sex, so it can be misleading for athletes, older adults, and some other groups. It's a general screening tool, not a diagnosis, talk to a doctor for a full picture of your health.
Frequently asked questions
Is BMI accurate for everyone?+
No. BMI doesn't distinguish muscle from fat, so very muscular people can register as "overweight" despite low body fat. It's a population-level screening tool, most useful as a rough starting point rather than a precise individual measure.
Does this tool store my weight or height?+
No. The calculation happens entirely in your browser. Nothing is saved or sent anywhere.