ANDY'S ANSWER:  A girl can expect her period somewhere between 2-3 years after the start of puberty. The first signs of puberty is when the breasts start developing. The average age to start puberty is 11 and the average age to start your period is 13. However, some girls can be a couple years earlier than that and others are a couple of years later than that. Nature knows when your body is ready you just have to be patient.