What Do the Percentiles on Child Growth Charts Mean?

As your child grows throughout childhood, you will receive ongoing information about her rate of growth from physicians who consult growth charts. Growth charts present this information to help physicians measure and track a child's growth. While growth charts can provide important information, this information should not be the only diagnostic tool a physician uses, warns the Centers for Disease Control and Prevention. Analyzing percentiles will give you information about how your child is growing.

A close-up of a doctor measuring a baby's foot while sitting on the examination table. (Image: AVAVA/iStock/Getty Images)

Comparing with Percentiles

Growth charts contain a set of percentiles ranging from 5 percent to 95 percent. Physicians measure a child's head circumference -- for children younger than age 3 -- weight and height. After gathering this data, the physician will plot it on the growth chart according to your child's age. With the weight, height and head circumference entered on the chart, it will indicate the percentile into which the data falls. The percentiles compare your child with other children. Higher percentages indicate a larger or taller child and lower percentages indicate a smaller or shorter child. For example, a girl in the 75th percentile for weight would be larger than 75 girls out of 100 and smaller than 25 girls out of 100. Percentiles also enable a physician to compare height to weight to determine proportionate growth. A child with 90th percentile weight and 25th percentile height is likely carrying too much weight for her height; whereas, a child in the 50th percentiles for both height and weight has an even proportion.

CDC Charting Historical Growth

The CDC created growth charts available for children from birth through age 20. CDC growth chart percentiles describe the growth of children in the United States during the 1970s and 1980s, according to the Washington State WIC Nutrition Program. When you receive percentile information based on your child's growth as plotted on a CDC growth chart, this information is providing you historical data that helps you see how your child compares to how children have grown in the U.S. CDC growth charts are appropriate for diagnostics for children older than 2.

WHO Charting Favorable Growth

The World Health Organization also has growth charts available, but the percentiles in WHO growth charts represent different information. Percentiles in WHO growth charts represent how children should grow in optimal environments without including factors of ethnicity, time or place, states the Washington State WIC Nutrition Program. The CDC recommends using WHO growth charts for children from birth to age 2.

Following the Curve

The percentiles on a growth chart create a curve. As a child grows, plotting the weights and heights on the chart will indicate whether a child is following a curve, which means that the child is remaining near or at the same percentile. Following a curve indicates a pattern of healthy growth. Even a 5th percentile can be appropriate for a child if the child follows this percentile curve consistently. The same is true for a child following the 90th percentile. A child at the 5th percentile is just smaller than average, and a child at the 90th percentile is just larger. If a child's growth pattern suddenly changes and weight drops or increases significantly in the percentiles, a physician may look for reasons behind the shift.