BMI (Body Mass Index) Calculator
Body Mass Index (BMI) is a guide for determining whether a person is underweight or overweight based on their height and weight. Figure out your child's Body Mass Index (BMI) to determine if your child is at risk.
A child's body fatness changes as they grow and differs for boys and girls. Once you have calculated your child's BMI, view the charts below to determine if your child is overweight or underweight based on his or her gender and age.
Using the CDC Growth Chart
Each of the BMI charts contains a series of curved lines indicating specific percentiles. The percentile curves show the pattern of growth for your child from preschool years into adulthood. BMI increases from early childhood into adulthood.
To find your child's BMI-for-age percentile, first click on the gender specific chart below. Then find your child's age on the horizontal scale (bottom of chart), and follow a vertical line to the BMI on the left.
| Boys, 2 to 20 years |
Girls, 2 to 20 years |
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Understanding BMI-for-Age Percentiles
The following guide can be used to identify underweight and overweight children and adolescents.
Please be aware that BMI doesn't directly measure body fat, and it is possible to be overweight but not obese. People who are athletic and have large muscle mass, may be overweight, but do not have excess body fat. In this instance they are normal. This is the exception. The majority of children who are overweight are also obese and need help with weight management.
Underweight
BMI-for-age < 5th percentile
If your child has a BMI-for-age that is lower than the 5th percentile, he or she is at risk of being underweight. This can be perfectly normal if your child is growing and developing normally, maintains a healthy diet and is physically active. However, if your child is not gaining weight or recently lost weight, has diarrhea, vomiting, poor appetite, an unhealthy diet, or low energy level this could be a warning sign and worth a full medical exam. Being underweight can also be a sign of an eating disorder, especially if accompanied by concerns about losing weight, poor self-body image, excessive exercise, or loss of regular menstrual cycle. Consult your child's physician if you suspect a medical condition causing him or her to be underweight or if you suspect an eating disorder.
Overweight
BMI-for-age > 85th precentile
If your child has a BMI-for-age that is equal to or higher than the 85th percentile, he or she is overweight. It is possible to be overweight without being obese, as is the case with athletes. If your child is overweight, is very active with no excessive fat, then he or she is normal. It is important for children in this category to maintain a healthy diet and remain physically active. Annual screenings with a physician are important to monitor the child's weight in relation to his or her growth an development.
Obese
BMI-for-age > 95th percentile
Children with a BMI-for-age equal to or higher than the 95th percentile are considered obese. They are at higher risk for becoming obese adults and increased risk for chronic diseases later in life, including cardiovascular disease and diabetes. A physical exam with your child's physician is advised to determine the best course of action and rule out any potential medical conditions.
The data for the BMIs for overweight children aged 2-20 and adults was adapted from the current guidelines as released by the Center for Disease Control's (CDC) National Center for Chronic Disease Prevention and Health Promotion.
Important: This information is not intended to substitute or replace the professional medical advice you receive from your child's physician. The content provided on this page is for informational purposes only, and was not designed to diagnose or treat a health problem or disease. Please consult your child's physician with any questions or concerns you may have regarding a medical condition.