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Overweight and Physical Activity Among Children:  A Portrait of States and the Nation, 2005
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BMI and Weight Categories for Children

Calculating Body Mass Index
The Body Mass Index (BMI) is a number that shows body weight adjusted for height and can be calculated using the following formulas:
 
English Formula
Weight in pounds ÷ Height in inches ÷ Height in inches x 703 = BMI
 
Metric Formula
Weight in kilograms ÷ Height in meters ÷ Height in meters = BMI
BMI for children, also referred to as BMI-for-age, is gender and age specific. BMI-for-age is plotted on gender-specific growth charts, available from the Centers for Disease Control’s (CDC) National Center for Health Statistics, which contain a series of percentile curves.
Weight Categories for Children
 
Underweight
BMI-for-age < 5th percentile
 
Normal
BMI-for-age 5th percentile to < 85th percentile
 
At Risk of Overweight
BMI-for-age 85th percentile to < 95th percentile
 
Overweight
BMI-for-age ≥ 95th percentile
Determine Your Child's Weight Category
1.
Calculate your child’s BMI using one of the formulas above. BMI can also be determined
by looking it up on the CDC Table for Calculated Body Mass Index Values for Selected Heights
and Weights for Ages 2 to 20 in which BMI has been calculated.
2.
Click on your child's gender below. You'll be taken to the CDC Web site where you can plot your child’s BMI on the BMI-for-age chart to determine his or her percentile-range.
Boy (Ages 2 to 20)
Girl (Ages 2 to 20)
3. Use the table shown above to determine the weight category.
More information on BMI is available through the CDC Web site.

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This chartbook is based on data from the National Survey of Children's Health. Suggested citation: U.S. Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Bureau. The National Survey of Children's Health 2003. Rockville, Maryland: U.S. Department of Health and Human Services, 2005.