When is your fertile window? Everything you need to know

You may have heard of the fertile window — the few days during each menstrual cycle around ovulation when you are most likely to conceive. Whether you’re trying to get pregnant or not, knowing when this period is can be helpful. It can help you better understand your body and any symptoms you get each cycle. The good news is, if you know what to look out for, it can be easy to track when you’re ovulating and when your fertile window is.

So, what should you look out for to identify your most fertile days? Let’s dive in.

H2: Key takeaways about your fertile window

• Ovulation is the moment in your cycle when one of your ovaries releases an egg. 
• Your fertile window is classed as the five days before you ovulate and one day afterward. This is because your egg remains viable for up to 24 hours after it’s been released, and sperm can live inside your body for up to five days after sex. 
• Tracking your cycles when you’re likely to ovulate can help you better understand your body and any signs or symptoms you experience each cycle. 
• There are a few different ways you can track ovulation and your fertile window. You can use an app like Flo to monitor your basal body temperature, keep an eye on changes to your discharge, or use ovulation tests.
• Some people also report feeling different around the time of ovulation. You might notice cramping or light bleeding, known as spotting. 

What is the fertile window? 

To best understand your fertile window, it can be handy to break down your cycle into two phases: the follicular phase and the luteal phase. Your follicular phase starts on the first day of a new period and lasts up to the point when one of your ovaries releases an egg. 

This can be timed differently for all of us, but in a typical 28-day cycle, this can happen around day 14. It’s known as ovulation and is a big milestone, as this is when a sperm has the chance to meet your egg and fertilize it. 

After an egg is released from one of your ovaries, it remains viable for up to 24 hours. Similarly, sperm can live inside your body for up to five days after sex. This means that even if you don’t have sex on the day you ovulate, you could still conceive. This period is known as your fertile window. 

How long is the fertile window? 

To establish how long your fertile window is, you just need to do a little bit of cycle math. You ovulate on one day of your cycle, and then that egg remains viable for up to 24 hours. Since sperm can live for five days in your body after sex, that means that your fertile window can last for almost a full week each month. 

Everyone’s cycles are slightly different, though, so it can be tough to track your fertile window every month. “Where the fertile window lands can fluctuate with every cycle,” says Dr. Jenna Flanagan, assistant professor of obstetrics and gynecology at the University of Utah, US. From hormones to stress, the length and regularity of your menstrual cycle and, therefore, your time of ovulation can be affected by several factors. 

Similarly, Dr. Flanagan explains that the health of your partner’s sperm can impact how long your fertile window is. “If sperm are unhealthy or are prematurely dying, then this would impact the length of time, specifically in the front end of the fertile window,” she says. 

How to calculate your fertile window

Because the fertile window can change every cycle, it’s useful to know the signs of ovulation. The good news is it’s quite easily done. 

1. Track your period 

Start on the first day of a new cycle. This is easily spotted as it’s the first day of a new period. Take note of the date this period starts. Then, wait and take note of the date your next period starts. This will give you your cycle length. You can do this using a notebook, calendar, or a cycle-tracking app like Flo. 

The average menstrual cycle is 28 days, but we’re all slightly different. If yours lasts between 21 and 35 days, then it’ll still be considered to be typical. 

2. Identify ovulation

In an average 28-day cycle, ovulation will occur a week after the end of your period (around day 14). As every cycle is different, it can be hard to predict exactly when you might be ovulating. Keep reading to learn how you can do this easily at home. You can also use an ovulation calculator to get a better idea of when this might be for you. 

3. Count your fertile days

Once you know the day you ovulated, you can count back five days before and one day after to deduce your fertile window for that cycle. This means that knowing your fertile window retrospectively is much easier than predicting it before it’s happened. However, it isn’t impossible. 

You might be in your fertile window when …

• Your cycle-tracking app alerts you: If the idea of keeping track of the dates of your periods and all of your symptoms feels overwhelming, then don’t worry. An ovulation-tracking app like Flo can do the math for you. All you need to do is log your period dates for a couple of cycles, and an algorithm will predict your ovulation days for you. 

  With Flo, you can easily log these symptoms and learn more about why they happen, so you’ll become a pro at spotting your likely fertile window in no time! You can also log your basal body temperature (BBT) and ovulation test results, keeping all that important information in one place.

• Your basal body temperature shifts: Did you know that ovulation can make you slightly warmer? Basal body temperature (BBT) is your temperature when your body is completely at rest. Just after you ovulate, your BBT increases by 0.4ºF to 1°F (0.22ºC to 0.56°C). So, measuring your BBT every day — using a special thermometer with two decimal places — can help you learn when you tend to ovulate.

• Your vaginal discharge changes: Just before you ovulate, your discharge (also known as cervical mucus) goes through some changes. Throughout the first half of your cycle, the cervical mucus will be thick, white, and dry. Then, just before and during the day of ovulation, it will turn clear and slippery, a bit like raw egg whites. This is to help make it easier for sperm to swim through your reproductive tract and meet an egg. Clever, right? 

  The egg white discharge usually lasts for about four days, signaling that it’s time to have unprotected sex if you’re trying. After ovulation, your discharge will become drier until you get your period a couple of weeks later. 

• You get a positive ovulation test: Ovulation predictor kits can take the guesswork out of tracking ovulation by confirming when you’re about to release an egg. If you use them correctly, these tests can be up to 99% accurate. These tests look for luteinizing hormone (LH), which is the hormone that makes your ovaries release an egg. LH surges 24 to 48 hours before you ovulate, so by detecting this surge, ovulation tests can tell you when you might be in your fertile window.

Using a combination of these methods is called fertility awareness and can help you to get a good idea of when you might ovulate and some of the symptoms that are typical for you. 

Changes to your BBT and discharge are two big signs you can look out for each cycle that may suggest ovulation is just about to or has just happened. However, some people also report feeling different symptoms, which can mimic how you feel just before your period starts. 

• Cramps: You might feel a slight ovulation pain in the lower part of your abdomen at this point in your cycle. Remember that you’ll only feel this pain on one side, depending on which ovary has released an egg that month.
• Light spotting: You might notice some spotting during ovulation. This is light bleeding between your periods that can appear as drops of blood when you wipe.
• Breast soreness or tenderness: The rush of hormones before and during ovulation may mean your boobs feel tender or sore. 
• Sex drive changes: Just before ovulation, there is a rise in the levels of a hormone called estrogen, and this can mean that you may start to feel more turned on than usual.