Length for girls at 8 months

At 8 months, the median length for girls on the WHO Child Growth Standards is 68.7 cm (27.1 in): half of girls this age measure less and half more. The middle half of girls, from the 25th to the 75th percentile, falls between 67.2 and 70.3 cm, a spread of 3.2 cm. The outer lines of the chart, the 2nd and 98th percentiles, sit at 64.0 and 73.5 cm.

Since 7 months, the median has risen by 1.5 cm in one month. By 9 months it reaches 70.1 cm. That monthly change is less than half the 4.5 cm of the first month, because growth slows steadily through the first two years.

For boys at 8 months the median is 70.6 cm, 1.8 cm more than for girls, which is why the charts are drawn separately by sex.

On the older CDC 2000 infant charts, which some clinics and websites still use before age 2, the median at 8 months is 68.4 cm. A girl exactly on the WHO median would read as about the 54th percentile there, one reason two charts can give different answers for the same length.

Reading the table: a girl at 8 months who measures 69.5 cm is at about the 62nd percentile, meaning that out of 100 girls this age, about 62 measure less. Under 2, this is length measured lying down. If a child under 2 was measured standing, WHO adds 0.7 cm before comparing.