Inputs changed, press Calculate BMI to update.
—
—
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 adult BMI categories (WHO)
- Below 18.5. Underweight
- 18.5 – 24.9. Normal weight
- 25.0 – 29.9. Overweight
- 30.0 and above. Obese
These categories apply to adults aged 20 and above. BMI doesn't account for muscle mass, bone density, or other individual factors, 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.
Why don't I see a category for ages under 20?+
The standard Underweight/Normal/Overweight/Obese thresholds are calibrated for adults. For children and teenagers, BMI is properly interpreted using age- and sex-specific growth charts instead, a fixed adult cutoff isn't medically appropriate for a growing body, so this tool shows the BMI number without a misleading adult category label.
Does this tool store my weight or height?+
No. The calculation happens entirely in your browser. Nothing is saved or sent anywhere.