When Does Ovulation Occur?

The menstrual cycle is the monthly series of changes that a woman’s body goes through to prepare for the possibility of getting pregnant. The release of an oocyte (immature egg) from the ovary is an essential part of this process.

The luteal phase is the second half of your menstrual cycle. It starts after ovulation and ends with the first day of your period. 

The 101: What Is Ovulation?

During reproductive ages in the human menstrual cycle, the ovary releases an egg every month. This event occurs when ovary follicles rupture and release the oocyte which travels to the fallopian tube and becomes an ovum or egg. 

The rupture of the ovary follicles can cause some light spotting and some women can even feel it happen. However, for the vast majority of women, the moment of ovulation goes unnoticed.

The process of ovulation is controlled by the hypothalamus of the brain and through the release of hormones. This means that ovulation can be impacted by hormone levels and stressors. From jet lag to thyroid disorders, the sensitive process of ovulation can be disrupted when your body undergoes changes. Hormonal contraceptives inhibit ovulation to prevent pregnancy. 

After the oocyte is released from the ovary, it moves into the fallopian tube. At this point it is called an ovum or egg. The egg stays in the fallopian tube for about 24 hours, waiting for a single sperm to fertilize it.

If the egg is not fertilized by sperm during that time (and pregnancy does not occur), it disintegrates (breaks down) and menstruation (your menstrual period) begins 11–16 days later.

Ovulation and Pregnancy: The Fertile Window

For many women, impending ovulation is an unnoticed process in their menstrual cycles. However, for women hoping to get pregnant, knowing when you might be ovulating is key to optimizing natural fertility and family planning.

Your most fertile days (the “fertile window") are the 3 days leading up to and including ovulation. This is when you’re most likely to get pregnant. So, having sexual intercourse then gives you the best chance of ensuring the egg is fertilized by sperm so pregnancy occurs.

But, as previously mentioned, ovulation and the menstrual cycle as a whole is a delicate process. Sperm heath is also key in your chances of getting pregnant. Not to mention, the woman's reproductive cycle is another variable factor. 

As most women will attest, your menstrual cycle can be impacted by stress, exhaustion, or emotional events (like grief.) Moreover, nutrition, cigarette smoking, and seasonal changes can also impact ovulation and therefore fertility.

This is one of the reasons birth control doesn’t just focus on ovulation. When the realities of life kick in, the fertile window can be a bit of a moving target. As we all know, our bodies don’t always follow the rules and irregular ovulation is a fact of life ;)

When Does Ovulation Happen in the Menstrual Cycle?

Every woman’s cycle is different. Some of us have longer periods than others, for example. So the timing of ovulation is not always the same in every woman's cycle.

But generally a woman’s entire menstrual cycle is on average 28 days. That said, it can range between 21 to 35 days in adults and from 21 to 45 days in young teenagers. That's why most women track their own cycle with a period calculator or diary—especially if they're hoping to achieve pregnancy.

The first day of a menstrual cycle is counted from the first day of your menstrual period. You ovulate about 14 days before your period starts.

If your average menstrual cycle is 28 days and the first day of your cycle is day 1 of your menstrual period, day 14 in your cycle is your day of ovulation, and your most fertile days are days 12, 13, and 14. These are the days pregnancy is most likely to occur.

If your average menstrual cycle is 35 days, ovulation happens around day 21 and your most fertile days are days 19, 20, and 21.

What Are the Telltale Signs of Ovulation?

Your Basal Body Temperature Falls

Your basal body temperature drops a little bit just before an oocyte is released from your ovary. Then, 24 hours after it is released, your basal body temperature rises and stays up for several days. 

According to Healthlink BC your temperature averages between:

• 36.1°C (97°F) to 36.4°C (97.5°F) BEFORE ovulation and
• 36.4°C (97.6°F) to 37°C (98.6°F) AFTER ovulation 

Fertility awareness-based methods (i.e., the rhythm method) of natural family planning rely on "tracking a woman's menstrual cycle, monitoring basal body temperature and watching for changes to cervical mucus," according to Cleveland Clinic.

However, fertility awareness-based methods necessitate paying close attention to your menstrual cycles for the best chance of success optimizing natural fertility. 

Cervical Mucus Changes When You Ovulate

As mentioned, the changes in your cervical fluid over the course of your menstrual cycle also hold clues about when you might be ovulating.

If your cervical mucus is...

• Dry or sticky: It’s unlikely you’re ovulating
• Creamy: You may start ovulating soon
• Wet or watery: You may start ovulating soon
• Wet and stretchy (egg white texture): You may be at your day of ovulation

It’s worth noting that cervical mucus is just one component of vaginal discharge, which can also include vaginal lubrication, arousal fluid, and more.

Again, making such observations is not an exact science and no woman’s body is a clock. But if you keep a period diary and ovulation calendar, it might be worthwhile to also note any observable changes to cervical mucus. Over time, you may see a pattern emerge.

Your Cervix Softens and Opens Up

As you approach your most fertile time, your cervix softens. This is sometimes known as having a short, high, open, and wet cervix (SHOW). 

For a step-by-step guide to checking your cervix position, visit this guide on Flo’s website. 

You May Experience Slight Twinge or Cramping

Mittelschmerz translates literally as “middle pain” and is the name for the slight twinge or cramp that some women experience when the follicle releases the oocyte on the day of ovulation during their menstrual cycle.

For many women, there is no ovulation pain whatsoever. 

The pain will occur on one-side of your lower abdomen. Because you have ovaries on 2 sides, the pain will switch sides each month, distinguishing it from the uterine cramping associated with menstruation.

According to the Mayo Clinic “Mittelschmerz pain occurs on the side of the ovary that's releasing an egg (ovulating). The pain may switch sides every other month, or you may feel pain on the same side for several months. Keep track of your menstrual cycle for several months and note when you feel lower abdominal pain. If it occurs mid-cycle and goes away without treatment, it's most likely mittelschmerz.”

If the ovulation pain is more severe, you should seek medical advice from a healthcare professional.

Some Light Spotting May Occur When You Ovulate

When the ovaries release the oocyte, a tiny follicle ruptures to allow it to be released. This can be a cause of spotting for a day or so.

For some women, spotting that occurs around the time of ovulation is light red or pink in color. This is because we also produce more cervical fluid around the time of ovulation and the blood gets mixed with that fluid, causing it to be a lighter shade.

Increased Libido or Sex Drive

The most well-known sign of ovulation is an increased sex drive. This is thought to be an evolutionary reaction to increase the likelihood of pregnancy. It’s important to note that this does not mean you’ll only want to have sex during ovulation. But it may definitely mean that you may experience an increased libido when ovulation occurs.

According to a report on Psychology Today, "ovulating women do clearly increase their sexual desire, and they do increase the frequency with which they have sex with their current partners.”

How Long Do You Ovulate For?

Ovulation, or the fertile window, lasts between 12 and 24 hours. That's how long the egg released by the ovary is viable for fertilization.

How to Know Your Fertile Window: Ovulation Predictor Kits

In addition to tracking the signs of ovulation listed above, there’s another step you can take to predict ovulation. This is especially helpful for those struggling with getting pregnant, who need to identify the fertile window.

An ovulation kit (also sometimes called an OPK, which stands for ovulation predictor kit) is a test that detects the presence and concentration of luteinizing hormone (LH) in your urine. Between 12–48 hours on average before ovulation, there is a brief surge in LH levels.

Ovulation predictor kits may be especially helpful for women trying to get pregnant or increase their fertility awareness, but who have irregular cycles. However, again the body can find ways to fool such methods...

According to the American Pregnancy Association, “When taken correctly, ovulation tests are approximately 99% accurate in detecting the LH surge that precedes ovulation. However, these tests cannot confirm whether ovulation actually occurs a day or two later. Some women may have a surge in the LH hormone without releasing an egg. This condition is known as luteinized unruptured follicle syndrome (LUFS).”

Your Ovulation Calculator

"Fertile windows are different for every woman and can be different from month to month in the same woman. Learn more about your fertility if you are trying to get pregnant,” the Office on Women's Health suggests.

Learning when you ovulate means you can predict when you’re likely to be fertile. More generally, it helps you become more familiar with your own body. This can help you appreciate the wondrous complexity of your body, but also notice any changes that might need medical attention from a healthcare provider.

Online calculators give approximate ovulation dates and fertile times for women who have regular periods.

Written by Jane Flanagan — Updated on April 5, 2022.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.