How old do you have to be to get your period?

Varies. There is not certain age. It sems to be younger and younger. Girls 7-8 years old are having menses. It is usually 10-13 years of age but may be as late as 14-16. If you are in good health and growing and developing normall and eating a normal diet and have not particular health issues, don't worry, it will come. If you go to 14 and not having menses, talk with your parents about seeing a doct.
It varies. The average age is 12 for menstruation. But girls can start much younger than that and as late as 14 yr is normal.