BMI Calculator

For help with dieting, nutrition, getting fit, weight loss, and managing obesity, see our Weight Management Guide.

The following body mass index charts are in full color and available for children aged 2 to 20 years old.

for girls		for boys
adapted from the United States Centers for Disease Control and Prevention, National Center for Health Statistics.

Notes on Calculate BMI results:

Related Topics Weight Loss Guide Exercise Guide Eating Disorders Kids BMI Calculator

Being overweight means that you or your child has a body mass index that is above the 95th percentile for his or her age. A body mass index that is above the 85th percentile for his or her age puts your child at risk of becoming overweight. Since body mass index doesn't directly measure body fat, it is possible to be over weight but not obese. Some kids who are very athletic and have a large muscle mass, may be overweight, but if they do not have excess body fat, then they do not need help with weight loss. However, the vast majority of children who are overweight are also obese and do need help with weight management.

Being underweight or at risk of being underweight means that your child has a body mass index for his age that is lower than the 5th percentile. This can be normal, especially if your child has been growing and developing normally, has a healthy diet, and is active and energetic. However, being underweight can also be a sign of a problem and deserves a full medical exam, especially if your child is not gaining weight or has recently lost weight, has diarrhea, vomiting, poor appetite, an unhealthy diet, or a low energy level. Children that are underweight can also be at risk of having eating disorders, especially if your child is overly concerned about losing weight, has a poor self body image, exercises excessively, has stopped having periods, or is using laxatives to lose weight. You should see your doctor if you suspect that your child has a medical condition causing him to be underweight or if you suspect an eating disorder. See the Eating Disorders Guide for more information.

For adults, a body mass index:

• over 30 is considered obese.
• between 25 and 29.9 is considered overweight.
• between 18.5 and 24.9 is considered a healthy bmi.
• under 18.5 is consider underweight.

The data for the BMIs for overweight children aged 2-20 and adults was adapted from the current guidelines as released by the CDC.

Our BMI Calculator was recently updated to allow entering a more accurate age for your child by adding a field for 'months'.

Important disclaimer: The information on keepkidshealthy.com is for educational purposes only and should not be considered to be medical advice. It is not meant to replace the advice of the physician who cares for your child. All medical advice and information should be considered to be incomplete without a physical exam, which is not possible without a visit to your doctor.