How do I know when my period will start?

Most girls get their first period around the age of 12

Most girls get their first period around the ages of 12 or 13, but some can be as young as 9 or as old as 16 (occasionally up to 18). There are some signs that will indicate your period might be on it's way such as white vaginal discharge (which is perfectly normal!), cramps in your lower stomach and back, mood swings (you might feel upset for no reason) and bloating. These are all perfectly normal and something you shouldn't be worried about. Your period will come once puberty has started, so you may notice other signs first, like developing breasts, pubic hair and pimples as well a rapid growth in your height and weight.