Body Mass Index (BMI) is calculated from a child's weight and height. BMI is a reliable indicator of body fat for most children and adolescents. Your child's pediatrician should assess BMI at each well visit beginning at age two.For children and adolescents, BMI is age- and sex-specific and is often referred to as BMI-for-age.

After BMI is calculated for children and teens, the BMI is plotted on the CDC BMI-for-age growth charts (for girls or boys) to obtain a percentile ranking