BMI Calculator for Kids & Teens

Adult BMI uses fixed cutoffs (e.g., BMI 25 = overweight) for all adults. Children's BMI-for-age uses percentile rankings because healthy body fat varies significantly with age and sex during childhood and adolescence. A BMI of 18 might be healthy for a 10-year-old but underweight for a 17-year-old. The CDC growth charts compare a child's BMI to thousands of children of the same age and sex, making it much more meaningful than a raw BMI number.

According to the CDC, weight categories for children and teens are: Underweight = below the 5th percentile; Healthy weight = 5th to less than 85th percentile; Overweight = 85th to less than 95th percentile; Obese = 95th percentile or above. The 50th percentile means your child's BMI is at the median — exactly average for their age and sex. A healthy weight percentile of 5–84 is considered normal for children.

BMI is a screening tool, not a diagnosis. Children who are very muscular or have larger frames may have a high BMI without excess body fat. Similarly, children going through a growth spurt may temporarily have higher BMI. If your child's BMI is at the 85th percentile or above, speak with your pediatrician — they can assess whether it's a concern based on full physical examination, growth history, and other health factors. Focus on healthy habits (balanced diet, regular play/activity) rather than weight loss in children.