BMI Calculator
Calculate adult BMI or age-appropriate BMI for children and teenagers
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months
This selection does not change the BMI formula; it selects the matching WHO growth reference. Use standing height, not lying length. WHO sources: ages 2–5 · ages 5–19
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Your BMI
Frequently Asked Questions
What is BMI?
Body Mass Index (BMI) is a measure of body weight relative to height: BMI = weight (kg) ÷ height² (m). It gives a quick indication of whether weight is in a healthy range — but does not account for muscle mass or body composition.
Why does the child calculator ask for age and a reference curve?
The BMI formula stays the same. For ages 2 to 17, the result is compared with the age-specific WHO reference for girls or boys because body composition changes during growth.
Can this calculator assess BMI for children?
Yes. Select the child and teenager mode to classify BMI using the international WHO reference for the exact age and selected growth curve. The result is a screening measure, not a diagnosis.