How often will I get my period? A menstrual cycle is counted from the first day of bleeding in one month to the first day of bleeding in the next month. The average menstrual cycle is about 28 days, but cycles that are 21–45 days also are normal. It may take 6 years or more after your period starts for your cycle to get regular. If you do this every month, you may notice a pattern. It may become easier to tell when you will get your next period.