What Is My BMI for Kids?

BMI stands for body mass index. It is a measurement of everyone's body fat, but there is a significant difference in the concept of BMI for adults and BMI for kids. The same equation is used, but the interpretation of the final numbers of the BMI for kids depends on the child's age, gender and other children's BMI, although the same three criteria are irrelevant in BMI for adults.

Measuring Height

The BMI formula is weight in kilograms divided by height in meters squared. You need to be more careful about making sure you measure your children's height accurately than your own, because they are growing. The Centers for Disease Control and Prevention has many recommendations for measuring height accurately, including unbraiding hair and removing bulky clothing, hair ornaments and shoes. Measure your kids' height to the nearest 1/8 inch.

Measuring Weight

Measuring weight accurately is also important because you need to estimate weight to the nearest 1/4 pound if you want to learn your children's BMI by using the CDC's BMI Percentile Calculator for Child and Teen. The CDC's recommendations for measuring weight accurately include making sure your kids stand in the center of the scale with both feet and asking them to remove their shoes and bulky clothes.

Calculating BMI

Find your kids' BMI by using the CDC's calculator or doing math. To figure out weight in kilograms, divide 2.2 into your child's weight in pounds. To figure height in meters, divide 39.4 into your child's height in inches.

Interpreting BMI

The meaning of your kids' BMI numbers depends on how they compare to children who are the same age and gender. Consult the CDC's calculator and charts on the agency's website. A 10-year-old boy is "underweight" if his BMI is lower than 95 percent of 10-year-old boys, "healthy weight" if his BMI is between his peers' fifth and 85th percentile, "overweight" if his BMI is between the 85th and 95th percentiles and "obese" if his BMI is higher than the 95th percentile.

Gender Differences

A boy and a girl with the same BMI are assessed differently. A 15-year-old boy and 15-year-old girl who are 5 feet 2 inches and 130 lbs. both have a 23.8 BMI. However, the girl is "healthy weight" because she is at the 83rd percentile among her peers while the boy is at the 86th percentile and "overweight." Men and women with the same BMI are both underweight when their BMI is under 18.5, healthy weight if it's between 18.5 and 24.9, overweight if it's between 25 and 29.9 and obese if it's 30 or more.