To use most period calculators, simply enter the date of your last menstrual period, how long your periods typically last and the length of your cycle, as evidenced by the period calculator created by Kotex. The calculator then provides you with the estimated date of your next period.
Using period-tracking software or marking the start and end dates of your period can help provide you with the information necessary to use this type of calculator. Some period calculators fulfill both the tracking and calculating roles. For example, Strawberry Pal claims that it starts with general calculations but gets more accurate as you use it to track your menstrual cycle over time.
You can use the information a period calculator gives you to help make plans, according to Ruby Cup. Period calculators can be fairly accurate for women with regular cycles, so you can use the information to make sure you have appropriate sanitary supplies with you. If there are things you prefer not to do when you are having your period, such as going on a date, you can avoid them.
If you are trying to get pregnant, period calculators can help you learn when you are ovulating. WebMD also suggests a similar tool called an ovulation calculator, although it cautions that these tools are only educated guesses and cannot be used to prevent pregnancy.