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Understanding Your Cycle and Calculating Your Fertile Window

Understanding Your Cycle and Calculating Your Fertile Window

Calculating your fertile window can be a tricky thing to do.

It is important to understand what is going on in your body to fully maximize your fertility window.

Check out these tips that will help you, hopefully, conceive.

graphic of uterus and hearts with text overlay

How do you Calculate Fertile Window?

So let’s take a few minutes to go through what’s going on in your body throughout your menstrual cycle. When we better understand what our bodies are going through throughout our menstrual cycle phases, we can better learn to pinpoint when ovulation should theoretically occur.

On average, a woman has a 28-30 day cycle.

For sake of numbers, we will use the twenty eight day menstrual cycle for this explanation.

What goes on within your uterus and ovaries varies during different parts and phases of your cycle.

Each phase can vary from woman to woman.

But, for the sake of trying to learn to understand your cycle. let’s base this off of a 28 day cycle and find the theoretical time of ovulation.

white pads opened on a red background

Menses Phase- the 1st phase of your cycle

The first day you get your period is considered day 1 of your cycle. Typically, an average period lasts 5 days.

So your period should theoretically be cycle day 1-5.

This is when your uterus is shedding then lining called the endometrium, that built up during the end of your last cycle.

The length of this phase of your cycle can vary from person to person and can vary from month to month.

Follicular Phase- the 2nd part of your menstrual cycle

The next part of the cycle is called the follicular phase.

Uterus and ovaries on a pink background.

What happens during the follicular phase of your cycle?

This is still prior to when ovulation happens and technically starts on day one of your cycle as well.

Theoretically, the follicular phase goes from day one to day thirteen of your cycle.

The follicular phase is when the endometrium, the lining of the uterus, thickens preparing for implantation.

It’s thickening to try to make a healthy home for a possible embryo.

What happens to the endometrium during this phase is very crucial to whether or not the uterus will be able to house and nourish a viable pregnancy.

The ovaries are deciding which one will produce the egg this month.

Generally, the ovaries take turns with which side will actually produce and release the egg each month.

This phase is called the follicular phase because important actions are happening in the follicles.

What are follicles and why are they important for ovulation?

Your ovaries are full of thousands of follicles throughout your life. Each month, theoretically, 1 follicle will be the “chosen one”.

As hormones change and fluctuate throughout your cycle, these hormones are helping the chosen follicle to increase in size each month.

The chosen follicle will hopefully grow large enough that month to release the egg and then it will become a corpus luteal cyst and will eventually dissolve and decrease in size once its job is done.

Occasionally, if hormones are feeling “extra productive”, they may pick two or more follicles to grow and release eggs. This is one way that twins can happen.

At the same time, if hormones are working “in overdrive”, this may cause the follicle to grow larger than it should.

This follicle may then release an egg, release an egg that may not be healthy or not even release an egg.

In fact, this follicle will continue to grow instead of “burst” when it should have/had released an egg and will become an ovarian cyst.

With increases and fluctuations in hormones, this ovarian cyst can continue to grow and become a problem.

Many females have experienced pain from developing an ovarian cyst.

Sometimes this cyst will grow so big that it ruptures on its own and can cause significant pain as well.

Other times, these cysts do not want to rupture on their own and will require some kind of medical treatment, like medication or surgical removal.

If hormones are all in line, a normal month will have the follicle increase in size, release a healthy egg and the follicle will decrease in size and degenerate into a corpus luteum which will continue to decrease in size and go away, making room in the ovary for other follicles to grow when they are “chosen”.

Some people choose to use ovulation test strips. These may help determine if your luteinizing hormone is increasing signaling that ovulation is coming soon.

However, these can not always be reliable, especially if you have an infertility diagnosis like Polycystic Ovarian Syndrome.

Sperm making contact with egg.
Sperm Attack

GO TIME- Ovulation

Mid cycle, cycle day 14 is theoretically when ovulation is to occur and an egg is released.

This is the theoretical fertile window! The ovulation window has arrived.

As you may or may not know, sperm can live up to five days, so in theory, your window is a few days before ovulation and a day or so after.

The egg can only live up to a day after it is released from the ovary before it meets up with the sperm.

So, having sperm on board before you actually ovulate, during the fertile window is OPTIMAL!

Learning when ovulation theoretically occurs for you personally is so important when trying to conceive.

What to do now?

Some doctors say you should have intercourse the day before and the day after this day, day 13 and 15 of your cycle, in order to make sure the egg meets with sperm and can begin the process to fertilize and work its way down the fallopian tubes and into a nice, thick endometrium for implantation.

Luteal Phase

After ovulation occurs, you enter the luteal phase. Typically, this is cycle day 15-28.

Here is when the endometrium continues to thicken and hopefully become the new home to a fertilized egg.

Now that you are a little more educated about how your cycle is made up of different components, you need to figure out exactly how long the different phases are for your personal cycle.

Some women have shorter cycles and phases or longer cycles and phases, changing the days that you would expect ovulation. Theoretically, you should ovulate around two weeks prior to your next period.

If I’m not on medication to regulate mine, I can have a cycle that comes once a month to once every three or four months.

Hello, trying to conceive hell!

Calendar to help with tracking ovulation.
Pregnancy test on paper calendar with red hearts

Tips for Tracking Ovulation

Writing down and tracking the length of your cycles and phases can help you figure yours out and will be something that your doctor needs to know, as well, if you are having trouble conceiving.

You can also chart your basal body temperature to pinpoint which cycle day you tend to ovulate each month.

Another thing you should also be tracking each cycle to determine fertility and point of ovulation is your type and amount of cervical mucous.

If you need more information on how to do that and what it means, check back, as I’m writing this out soon.

graphic of uterus and hearts with text overlay

So, you’re having trouble conceiving?

The stress may be taking a toll on you and your spouse.

If you’re looking to find easy and fun ways to reconnect with your spouse, make sure to check out the FREE printable that we offer.

You’ll gain access to our weekly email about all the fun things going on, as well as, some tips and tricks we may be learning along the way.

Make sure to take a look into the other factors that could be impacting your fertility.

Is it taking a toll on you mentally? If coping with your infertility diagnosis is something you’re having trouble with, I highly recommend you check out this e-book, Infertility is a Diagnosis, not a definition.

It’s an easy read and is written by someone who has been through infertility herself and has fought and overcome the battle with a successful pregnancy.

Reminder of how to find your typical ovulation window

  • Calculate the overall length of your cycle
  • Remember the different phases of a cycle
  • Find out when your personal window of when ovulation theoretically occurs
  • Track symptoms leading up to your typical ovulation window and after that window
  • Keep track in an app or calendar

I just wanted to share that having a healthier lifestyle helped my body learn to ovulate again on its own each month. If you’re interested in getting a healthier lifestyle, and prepare your body for pregnancy, why not try out this amazing pregnancy exercise course.

They offer a nutrition for pregnancy course as well. The things we eat and the way we exercise prior to becoming pregnant is just as important as how you take care of yourself throughout pregnancy.

Get a head start and start your pregnancy (or pre-pregnancy) exercise program now and see how eating properly and eating truly nutritious food can help you get pregnant and then help you during your pregnancy.

With a degree in Exercise Science and a career in the medical field, I truly love helping other people find a healthier lifestyle, which has lead me to sharing as much as I can about health, fertility and pregnancy.


Thursday 2nd of May 2019

This is not correct. Ovulation does not necessarily occur on CD14. It could happen that way, but it primarily does not. That's an extremely antiquated and incorrect way of thinking. Ovulation can occur on pretty much any cycle day.

Thursday 2nd of May 2019

While you are correct that ovulation doesn’t always happen on CD 14, you’ll see that I also said in the post that this is based on a typical 28-30 day cycle and the lengths of each phase of the cycle can differ from woman to woman. I also discussed ways to track the phases in your cycle to pinpoint your personal exact day of ovulation. I used those numbers for a point of reference as that’s what the medical field uses. Working as an Ultrasound Technologist, we use CD 14 as time of ovulation, for pelvic and pregnancy ultrasounds, knowing that it can vary person to person and depending on cycle length and phases as was discussed in the post.


Wednesday 7th of June 2017

Fantastic explanation! This is such empowering information for women to know.

Wednesday 7th of June 2017

Thanks for checking it out Bailey :) The more you know, the better! That's my motto

SArah ALthouse

Monday 5th of June 2017

My husband and I are trying to get pregnant and I've been looking for an article just like this to figure out when is the best possible time. thank you!

Monday 5th of June 2017

Best of luck to you Sarah! This can be quite a challenging time for some couples. We sure went through a lot to get pregnant with our daughter. If you have any questions about anything here, or fertility in general, feel free to email me at


Thursday 18th of May 2017

This is a great tutorial. I learned so much about my body when trying to conceive. It can be especially difficult with irregular cycles, like you described.

Friday 19th of May 2017

Tricia, I'm sorry you had troubles, but from your picture- I think you had success! Yayyyyyyyyy. I learned so much as well and figured I'd share for those who needed to learn more. Thanks for taking the time to read and comment :)


Saturday 22nd of April 2017

This post is great! I was surprised how little knew about my cycle before trying to get pregnant.

Saturday 22nd of April 2017

There's so much to learn. So much has to be correct with timing. I don't know how people get pregnant without trying sometimes lol. So much has to be right , it's amazing how the body works!