CDC has an online tool to calculate BMI for kids and teens (age 2 through 19). It displays numeric results, a graphic that shows the weight category, and plots the BMI on a printable growth chart.
Check BMI-for-age annually, or more often if recommended by the child’s healthcare provider. Tracking growth patterns over time can help you make sure your child is achieving or maintaining a healthy weight. A single BMI-for-age calculation is not enough to evaluate long-term weight status because height and weight change with growth. If your child has significant weight loss or gain he or she should be referred to and guided by a health professional.
Please keep in mind that this BMI calculator is not meant to serve as a source of clinical guidance and is not intended to be a substitute for professional medical advice. Since BMI is based on weight and height, it is only an indicator of body fatness. Individuals with the same BMI may have different amounts of body fat. Persons may consider seeking advice from their health-care providers on healthy weight status and to consider individual circumstances.