How to Find the Best Days to Conceive after Menstruation

You may have read that women ovulate on day 14 of their cycle or in the middle of their cycle. Ovulating in the middle of a cycle, however, is based on the average of when ALL women ovulate.

Using an average is not an accurate way to predict when you will ovulate.

"This is a myth [that women ovulate on day 14 of their cycle] that many, including healthcare professionals, still believe. The “14th day” thinking appears to come from either taking the average of when all women ovulate or from just dividing the 28 day cycle in half. This is not an accurate way to calculate ovulation because many women do NOT ovulate on the 14th day of their cycle." - American Pregnancy Organization

There is substantial variation not only between you and other women, but your ovulation day can also be different from month to month. Research shows that ovulation can occur anywhere between 8 to 20 days [1]. This is why using an app or ovulation calculator alone is not a reliable method to find your fertile days.


Phases of the Menstrual Cycle

Knowing about your menstrual cycle length can help you determine your fertile window and may lend useful information about your fertility.

Determine the Length of your Menstrual Cycle

This image shows a 28 day cycle with ovulation occurring on day 14. To figure out your cycle length, you can either use a regular calendar or a period tracker app.

A cycle length is determined by the first day you get your period until the first day of your next period. For example, if your period started January 1st, and then the first day of your next period lands on January 30th, your cycle is 30 days long. 

The Follicular Phase:

This phase plays a large role in how long your cycle will be. During this time, an egg follicle gets ready to release an egg. At the same time your uterus starts to prepare for pregnancy by growing a new endometrium (lining of the uterus which is shed if there is no fertilized egg).

The last 3-5 days of the follicular phase, plus ovulation day, is your fertile window.

The Luteal Phase:

This phase is from the time after you ovulate until you start your period. The length of this phase stays fairly consistent in each woman and does not tend to vary more than a day each month.

Knowing the length of your luteal phase can lend important information about your cycle. If your luteal phase is too short, for example, you may not have enough progesterone and therefore, not enough time for the fertilized egg to implant in the uterus.

Your luteal phase should be 10-14 days long.


To figure out the best day to conceive after your menstrual cycle, you can use several methods:

  • Use a product to find your fertile days and the day you ovulate (such as a temperature sensor, LH-hormone levels from urine or estrogen from your salvia). Vaginal core temperature is the most accurate way to identify when you ovulate.

  • Use a calendar or app to track your cycle length in conjunction to using other methods. Since timing is everything, keeping track of when your period will start and the length of your cycle will help to get the timing right.

  • Learn about your cervical mucus and watch for when it is clear and slippery which indicates that you are fertile.

  • If waking up the same time each morning does not seem too daunting, you may want to track your basal body temperature (BBT) to identify the day you ovulate.



[1] Geirsson RT (1991). "Ultrasound instead of last menstrual period as the basis of gestational age assignment". Ultrasound in Obstetrics and Gynecology. 1 (3): 212–9. doi:10.1046/j.1469-0705.1991.01030212.xPMID 1279