About this tool
Calculate BMI (weight in kilograms divided by height in meters squared) in metric or imperial units, and see where the result falls in the World Health Organization's adult categories: underweight below 18.5, normal 18.5–24.9, overweight 25–29.9, and obese 30 and above.
BMI is a population-level screening number, not a diagnosis. It cannot distinguish muscle from fat — muscular athletes routinely score “overweight” — and it does not capture fat distribution, which matters for health risk. Treat it as one rough signal, and rely on a healthcare professional for actual assessment.
How to use it
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI and the WHO category it falls into.
Frequently asked questions
What is a healthy BMI?
The WHO defines the normal range for adults as 18.5 to 24.9. Cut-offs differ for children and may be interpreted differently across populations.
Is BMI accurate for athletes?
Often not — muscle is denser than fat, so very muscular people can register overweight or obese while carrying little body fat.
Does this calculator work for children?
No. Child and teen BMI is assessed with age- and sex-specific percentile charts, not the adult cut-offs used here.