Your menstrual cycle starts between the ages of 8-15.
The average age in the United States for a girl to begin menstruation is 12 years old. Starting earlier or later is normal, but generally occurs about two years after breasts begin to develop.
How Is Your Menstrual Cycle Measured?
Your menstrual cycle is measured from the first day of your last period, to the first day of your next period. The average duration of the menstrual cycle is 28 days long but can range between 21-35 days for a healthy woman, and 21-45 days for a healthy teen.
When Does Your Menstrual Cycle End?
The average age that a woman enters menopause is at age 50. Onset of menopause can range between the ages of 45-55 and can last from 2-8 years.
“Menstruation and the menstrual cycle fact sheet | womenshealth.gov .” womenshealth.gov . N.p., n.d. Web. 9 Jan. 2012. <http://www.womenshealth.gov/publications/our-publications/fact-sheet/menstruation.cfm#f>.