Body Mass Index, BMI, is an age- and gender-specific measure calculated from a child’s height and weight and used as a screening tool to identify possible weight problems. After calculating BMI for a child, the BMI number is plotted on the Centers for Disease Control BMI-for-age growth charts for girls or for boys. The resulting BMI percentile ranking is a common indicator of growth of children in the United States. The American Academy of Pediatrics and the CDC recommend annual screening of children for overweight using BMI beginning at 2 years of age.
Step 1
Measure the toddler’s height in inches by having him stand up straight and still with his back to a wall and place one end of the measuring tape at the floor level and extend the tape up the wall to the level of the top of his head. Record the number of inches measured to the nearest 1/8 inch. For example, suppose a 3-year-old toddler boy measures 37.5 inches tall.
Step 2
Ensure the bathroom scales are accurate and set to zero. Weigh the toddler on the scales. Record the number of pounds to the nearest 1/4 pound. In the example, say the toddler weighed 32 lbs.
Step 3
Multiply the child’s weight in pounds by 703. For example, 32 lbs times 703 = 22,496.
Step 4
Multiply the measure of the toddler’s height in inches by itself to produce the height squared. For example, 37.5 inches times 37.5 inches = 1,406.3.
Step 5
Divide the number obtained in Step 3 by the number obtained in Step 4. The result is the child’s BMI. For example, 22,496 divided by 1,406.3 = 16.0. Therefore, in the example, the toddler’s BMI is 16.0.
Tips and Warnings
- The result can be plotted on the CDC Growth Chart titled “Body Mass Index for Age Percentiles, Boys 2-20 Years.” BMI is calculated the same way for children and adults, but is interpreted differently. Adult weight status categories do not apply to children and CDC growth charts apply only to children and adolescents ages 2 to 20 years. Age and gender-specific BMI percentiles apply to children because the amount of body fat normally changes with the age of a growing child and the amount of body fat normally differs between growing girls and boys. These differences are taken into account by the CDC BMI-for-age growth charts.
- BMI is only one indicator of growth in children and must be used in conjunction with other assessment methods and tools to track growth progress over a period of time. Consult a physician or dietitian for interpretations involving growth spurts, overweight and growth outcomes related to specific conditions or disease states.
Things You'll Need
- Measuring tape
- Bathroom scales
- Calculator
Member Comments