Free kids BMI calculator: get your child's Body Mass Index and CDC age-and-sex percentile with healthy weight range
A child's BMI is not read against adult cutoffs. Because body fat changes naturally as children grow, kids' BMI is compared against growth charts that account for age and sex.
Enter your child's age, sex, height and weight to get their BMI, the percentile they sit at among children of the same age and sex, and the weight range that would keep them in the healthy zone.
This calculator uses the CDC 2000 growth charts for ages 2 to 19 and is a screening tool, not a diagnosis. Always discuss results with your child's pediatrician.
Children are still growing, so their amount of body fat changes with age and differs between boys and girls. A BMI of 17 is healthy for a 8-year-old but underweight for most adults. That is why kids' BMI is expressed as a percentile that compares your child with others of the same age and sex, using the CDC 2000 growth charts.
It means that out of 100 children of the same age and sex, about 75 have a lower BMI and 25 have a higher one. The healthy range spans the 5th to 85th percentile. Above the 85th percentile is classified as overweight and above the 95th as obesity, following CDC definitions.
First remember this is a screening number, not a diagnosis. Muscle mass, recent growth spurts and measurement error all move the result. Bring the result to your child's pediatrician, who can interpret it alongside growth history, family background and a physical exam before recommending any changes to diet or activity.