BMI for girls at 9 years

At 9 years, the median BMI for girls on the CDC 2000 growth charts is 16.3 kg/m²: half of girls this age have a lower BMI and half a higher one. The middle half of girls, from the 25th to the 75th percentile, falls between 15.1 and 17.9 kg/m², a spread of 2.9 kg/m². The outer lines of CDC’s BMI-for-age chart, the 5th and 95th percentiles, sit at 13.7 and 21.8 kg/m².

Since 8 years, the median has risen by 0.5 kg/m² over 1 year. By 10 years it reaches 16.8 kg/m².

For boys at 9 years the median is 16.1 kg/m², 0.1 kg/m² less than for girls, which is why the charts are drawn separately by sex.

CDC uses BMI-for-age, not weight-for-length, from age 2. At 9 years the 85th percentile for girls is 19.1 and the 95th is 21.8 kg/m². Above the 95th percentile, CDC's 2022 extended charts replace the original curve, so the 99th percentile here is 27.0 kg/m², computed with the extended method.

Reading the table: a girl at 9 years with a BMI of 17.5 kg/m² is at about the 70th percentile, meaning that out of 100 girls this age, about 70 have a lower BMI.