Some estimates suggest that the median age of menarche worldwide is 14, and that there is a later age of onset in Asian populations compared to the West. The average age of menarche is about 12.5 years in the United States, 12.72 in Canada, 12.9 in the UK and 13.06 ± 0.10 years in Iceland.A study on girls in Istanbul, Turkey found the median age at menarche to be 12.74 years.ost sources agree that the average age of menarche in girls in modern societies has declined, though the reasons and the degree remain subjects of controversy. From the sixth to the fifteenth centuries in Europe, most women reached menarche on average at about 14, between the ages of 12 and 15.