Children’s BMI Calculator: Normal & Abnormal Ranges

​A body mass index (BMI) value for children is used to evaluate whether a child or teen is within their ideal weight. It can be used by pediatricians during wellness exams or by parents at home. 

A child's BMI looks at the relationship between weight and height for children aged 6 months to 18 years old. It assesses whether current weight is above, below or within range for their age, and can help to identify malnutrition or obesity. 

Normally, the pediatrician will use the BMI and consider the child or teen's age to determine whether they are developing as expected. Any abnormal or unexpected results can prompt a nutritional assessment to determine whether eating habits should be addressed.

How to calculate

To calculate a child’s BMI, use the following calculator:

years old

Usually, this calculation incorporates age to verify if the child is developing as expected. An abnormal value does not confirm a diagnosis, but it can prompt further investigation to identify whether possible dietary or activity changes are needed.

What to do if BMI is abnormal

An ideal BMI can be achieved through healthy lifestyle and dietary. These should be shared by the entire family to ensure success. 

How to increase BMI 

If BMI is below the normal range, you should have the child assessed by a pediatrician and registered dietitian to assess whether there are any factors contributing to weight loss. There may be nutritional deficiencies present, and a multi-disciplinary approach can help the child to regain weight. 

In general, weight gain can be promoted through a diet that is rich in protein and healthy fats. Health care professionals may also advise introducing a daily multivitamin or an additional meal supplement (like Pediasure) to the child’s diet, to ensure adequate calories are consumed. Check-out our list of high-protein foods that can be incorporated into the whole family’s diet

How to lower BMI

A high BMI may be a sign of being overweight or obese. Treatment is aimed at promoting healthy lifestyle habits and a diet that is low in sugar and fats. Parents and caregivers should provide opportunities for daily physical activity, while continuing to promote a positive body image. 

Treatment for weight loss should not be emphasized on just the child - it is important to evaluate the home environment and make positive changes that involve all members of the family. Children who are obese should be monitored by a multi-disciplinary team made-up of a registered dietitian, pediatrician and psychologist. This will help to ensure that lifestyle changes are therapeutic for the child and maintained throughout the lifetime.