Child BMI calculator
Your child's BMI number — and why a pediatrician reads it differently than an adult's.
BMI works very differently for children than for adults. This tool gives you the raw number — but the important part is understanding why that number alone can't tell you whether your child's weight is healthy.
The short answer: for kids and teens, BMI is read as a percentile for age and sex on a growth chart. Your pediatrician calculates and tracks that over time — so the value here is not a diagnosis or a weight-status category.
Calculate your child's BMI
Child BMI
Your child's BMI number — and why a pediatrician reads it differently than an adult's.
This is the BMI value only — not a diagnosis or a weight-status category. Children's BMI must be interpreted by age and sex by a healthcare provider.
Healthy Living for Kids & Teens →An adult's BMI maps straight onto fixed categories. A child's doesn't: the same number means something different at age six than at age fourteen, which is exactly why it has to be plotted by age and sex.
If you have any concern about your child's growth or weight, the right next step is a conversation with their pediatrician — they can interpret the percentile and the trend in context, which no single number can do.
Common questions
How is a child’s BMI different from an adult’s?
For adults, BMI maps directly to fixed categories. For children and teens it does not: the same BMI means different things at different ages, so it’s plotted as a percentile for the child’s age and sex on a CDC growth chart. A pediatrician calculates and tracks that percentile over time.
Does this calculator tell me if my child’s weight is healthy?
No. It gives the BMI value only — not a percentile, category, or diagnosis. Because interpreting a child’s BMI requires growth-chart data for their age and sex, only a healthcare provider can tell you what it means for your child.
I’m worried about my child’s growth or weight — what should I do?
Talk with their pediatrician. They track BMI percentile and growth over time and can interpret the trend in the context of your child’s overall health, which a single number never can.
This is general education, not medical advice, and not a diagnosis or weight-status category. A child's BMI must be interpreted by age and sex by a healthcare provider.