cdc.gov the average of 13.5–14 inches this page World Health Organisation http://www.cdc.gov/growthcharts/html_charts/hcageinf.htm http://www.cdc.gov/growthcharts/html_charts/hcageinf.htm the average of 13.5–14 inches http://www.cdc.gov/growthcharts/html_charts/hcageinf.htm