Why is there an adult and child mode?
Adults use fixed BMI ranges. Children and teens are growing, so BMI is compared with children of the same age and sex.
BMI Calculator
Calculate adult BMI, child and teen BMI percentiles, healthy weight range, BMI prime, and waist-to-height ratio with metric or US units.
BMI for adults, children, and teens
Use the calculator for a fast BMI result, then check the context that medical calculators usually separate across multiple pages: adult thresholds, child percentiles, healthy weight ranges, and waist-to-height ratio.
What it calculates
- Adult BMI category using standard thresholds.
- Optional lower adult thresholds used for some ethnic backgrounds.
- Child and teen BMI percentile by sex and age from CDC growth-chart data.
- Healthy weight range at the entered height.
- Waist-to-height ratio when a waist measurement is entered.
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BMI formula
BMI is weight divided by height squared. US units use the 703 conversion factor.
Metric
US units
Interpreting the result
- Adult BMI is intended for people aged 20 and older.
- Child and teen BMI must be interpreted by age- and sex-specific percentiles.
- BMI is a screening measure; it does not distinguish muscle, bone, water, and fat mass.
- Pregnancy, eating disorders, some disabilities, and conditions that affect height need individual clinical advice.
FAQ
Why are lower thresholds available?
Some medical guidance uses lower adult BMI cutoffs for people from Asian, Black African, African-Caribbean, or Middle Eastern backgrounds because risk can increase at lower BMI values.
Is BMI a diagnosis?
No. BMI is a screening tool. A clinician can interpret it with medical history, waist measurement, body composition, labs, and other health factors.
