The method actually relies on the women who have a regular 28 day cycle along with the ovulation that takes place exactly on 14th day midcycle. It’s absolutely necessary to avoid the intercourse for at least 3 days before and 3 days after the ovulation 11th day through 17th day at least, and optimally 7 days earlier and at least 4 days after. If this sort of regularity is not standard over a woman’s cycle, then it would be helpful to prefer another calendar method that takes cycle variance into its account.

First of all, accumulate the entire necessary details regarding the cycle length and first this purpose, you should take sufficient enough time for tracing out how wide actually the range is. It’s necessary for you to gain knowledge about the longest and shortest length of cycle that you experience 1st day being the very first of menses, and the last day being the one soon before the menses continues. Deduct 20 from the shortest length of cycle in order to get the very first day of fertility (4th day in the 24 days cycle). Deduct 10 from the longest length of cycle for getting the last day of fertility (22nd day in the 32 days cycle). Therefore, a woman undergoing cycles that range from 25-30 days have to avoid the intercourse from 5th day to 20th day. (25 _ 20 _ 5 and 30 _ 10 _ 20). In nutshell, with calendar methods, you need to keep the written record of each of your cycle and you’ll be able to determine where your conceiving chances is more by the help of that record.