Length for boys at birth

At birth, the median length for boys on the WHO Child Growth Standards is 49.9 cm (19.6 in): half of boys this age measure less and half more. The middle half of boys, from the 25th to the 75th percentile, falls between 48.6 and 51.2 cm, a spread of 2.6 cm. The outer lines of the chart, the 2nd and 98th percentiles, sit at 46.1 and 53.7 cm.

By 1 month it reaches 54.7 cm.

For girls at birth the median is 49.1 cm, 0.7 cm less than for boys, 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 birth is 50.0 cm. A boy exactly on the WHO median would read as about the 48th percentile there, one reason two charts can give different answers for the same length.

Reading the table: a boy at birth who measures 50.5 cm is at about the 63rd percentile, meaning that out of 100 boys this age, about 63 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.