The calendar method, also known as the rhythm method or fertility awareness, involves planning your sex life around your menstrual cycle. Avoid sex during ovulation--that sounds easy enough, right? Well, not really, according to statistics...
If you're considering the calendar method, here's what you have to know.
To be fair, the calendar method is almost as effective as the pill--but only with perfect use! During its safest, the calendar method is 98.2% effective. But, with typical use, it's between 76-88% effective. That means between 12 to 24 women out of 100 using the calendar method will get pregnant on average.
Perfect use not only entails strict dates for your frame of ovulation, but also a strictly regular period. For example, even if your period is relatively regular but fluctuates between a couple days early or late, it's more difficult to predict exactly when ovulation begins and ends. If you have unprotected sex during that supposedly "safe" date, you may have a problem.
There are actually four ways to implement the "calendar method." Also, not all of them require calendars:
The best way to use the calendar method, also known as the symptothermal method, is to use the temperature, cervical mucus, and calendar methods combined. All three together rank closer to "perfect" use.
No matter how you're tracking your period, Planned Parenthood recommends tracking your menstrual cycle for at least six periods before using the calendar method in order to be as familiar with your own cycle as possible. That would be six months with either no sex or using non-hormonal methods of birth control. Keep in mind that hormonal methods would mess with your cycle before you even finish observing it.Which, by the way...
With about one week of ovulation and another week of menstruation, that leaves about two weeks in a month in which you could have sex. So you would have to decide: do you have time for that? Well, some people combine methods. For example, some women use condoms during ovulation week.
But if you were looking for a reliable, easy birth control option, the calendar method isn't it. Most doctors suggest other forms of birth control methods before the calendar method because of both its high risk of unwanted pregnancy and lack of STI protection.