Calendar Method
What is it?
The calendar method helps you estimate the time of ovulation after you have charted the lengths of your menstrual cycles for several months.
How to Use
- Keep track of the lengths of your menstrual cycles for 6-12 months. Day 1 is the first day of your menstrual bleeding.
- After six or twelve months of data collection, find the length of the shortest and longest menstrual cycle.
- Subtract 18 from the length of your shortest cycle. This tells you the first fertile day in your average cycle. For example, if your shortest cycle is 24 days long, then your first fertile day would be day 6 of your cycle.
- Subtract 11 from your longest cycle. This will be the last fertile day in your average cycle. For example, if your longest cycle was 32 days long, then your last fertile day would be day 21 of your cycle.
- During this fertile period (e.g., Day 6 through Day 21) you must abstain from having unprotected intercourse.
Advantages
- It's free!
- It can be used with other methods of birth control, such as condoms, diaphragms, spermicides, etc.
- It is ideal for people who cannot use other methods of birth control for personal, medical, or religious reasons.
- If this method is used correctly it can give you a pretty good idea of when you will be ovulating so that you can avoid pregnancy by abstaining from sex.
Disadvantages
- It does not protect against sexually transmitted diseases.
- Is not as effective as other methods of contraception. In fact, it is the least effective of all the fertility awareness methods.
- You need to record your cycles for several months, ideally an entire year, before you can begin to use this method.
- This is not a good method for someone who is not willing to keep track of their cycles or practice abstinence for a few weeks out of every menstrual cycle.
- Do not use this method if your cycles are shorter than 27 days.
Cost
This method is practically free! The only things you may need to pay for are charts to record your cycles on and any fees for the classes that train you in this method.
Effectiveness
This method has a 9% failure rate among perfect users.