If you've been struggling to get pregnant, or want to time your pregnancy just right, you may benefit from using an ovulation calculator, also known as an ovulation calendar. An ovulation calculator will help you determine when you'll be ovulating, giving you the best day(s) for conception, or if you're using it for contraceptive purposes, the day(s) you should abstain from intercourse. Of course, as with any natural method of contraception, an ovulation calculator is by no means guaranteed.
Ovulation calculators work by taking the length of your cycle, and calculating the window of time that you may be ovulating. Most women have a 28 to 32 day menstrual cycle, and typically ovulate from around the 11th day to the 21st day of that cycle. Some ovulation calendars will give you anywhere from a three day to an eleven day window of time when you may be ovulating, increasing your odds of conception. Keep in mind that women who have shorter cycles typically ovulate earlier in their cycle, while women with longer cycles ovulate later. Some ovulation calculators also give you the earliest date that you can start taking pregnancy tests, based on when you should conceive.

An ovulation calculator may be as simple as counting eleven days from the first day of your period, or entering the length of your period and date of last menstrual period (LMP) online. If you choose to utilize an online ovulation calculator, it may give you one month or several months of predicted ovulation dates, as well as a window of time every month when you should try to get pregnant, as well as predicted due dates if you get pregnant that month. Remember that an ovulation calendar is based on the average woman's cycle — every woman is different, and each woman can even have a varied cycle from month to month. If you are very regular, you may be able to use an ovulation calculator that calculates several months in advance — but if you are not regular, you may want to take it one month at a time.

Ovulation calculators should not be confused with ovulation predictor kits, which are kits that test your urine for the presence of luteinizing hormone (LH). Most women will have a surge of LH 1-3 days before ovulating, and an ovulation predictor kit will read this and return a positive result. Since these can be pricey, and require more effort and consistency in taking it, you may want to stick with using a simple ovulation calculator for a few months. If the ovulation calculator doesn't help you get pregnant, then you may want to use an ovulation predictor kit as your next step. Be sure to ask your doctor for a recommendation on which type/brand she prefers.