What Is Ovulation? Definition, Causes, Symptoms, and More

Ovulation is when one of your ovaries releases a mature egg, typically occurring mid-cycle around day 14 in a 28-day cycle. The egg survives 12-24 hours and can be fertilized by sperm during this time. Your fertile window spans 6 days total: the 5 days before ovulation plus ovulation day itself, since sperm can survive up to 5 days in the reproductive tract.

If you're not sure when ovulation happens, why it matters for fertility, or how to know if you're ovulating, this guide has all the answers.

In this guide to ovulation, we cover all the topics you’ve been wondering about, including what is ovulation, what causes ovulation, does ovulation mean you’re fertile, when do you ovulate, how long does ovulation last, what are signs of ovulation, and how to tell if you’re ovulating.

Ovulation definition

Ovulation is the moment during your menstrual cycle when one of your ovaries releases a mature egg. That egg doesn’t appear out of nowhere, though: prior to ovulation, it grows in a follicle in your ovaries for a couple weeks (more on that below).

Once the egg is released, it flows down along the fallopian tubes, where it hangs out for around 12 to 24 hours. Now, one of two things can happen:

• Fertilization: If the egg runs into sperm during this time—either new sperm or sperm that’s been in the reproductive tract for a few days (which is totally normal and safe!)—the egg can be fertilized. From there, the fertilized egg travels to the uterus, implants in the uterine lining, and becomes a pregnancy about two weeks post-ovulation.

• No fertilization: If the egg doesn’t get fertilized, it reaches the end of its viability about one day post-ovulation, then disintegrates and is absorbed into your body. From there, your period comes about two weeks afterward and the menstrual cycle restarts.

Pretty straightforward, right? Well, sort of.

What causes ovulation?

Ovulation may seem pretty cut and dry on the surface: you move through your menstrual cycle, your ovaries release an egg, and that’s that! 

But really, there’s a lot going on behind the scenes to make ovulation happen. The star players are your hormones, including follicle-stimulating hormone (FSH), estrogen, and luteinizing hormone (LH). 

Your body starts setting the stage for ovulation during your period, meaning as early as the first phase of your menstrual cycle (the follicular phase).

While you’re on your period, glands in your body start producing FSH. FSH tells your ovaries to begin making follicles, which house immature eggs (or oocytes). One follicle soon becomes dominant, and the egg it holds grows to full maturity. 

As the egg grows, it releases estrogen. Rising estrogen triggers the uterine lining to thicken in preparation for a potential pregnancy. Estrogen also tells your body to lower FSH levels and increase LH levels.

When LH hits its peak level, also called the “LH surge,” your ovaries receive the signal that it’s time to release the now-mature egg. Then, ovulation happens: the egg is released, and is either fertilized or disintegrates.

Finally, a rise in progesterone signals the end of ovulation. If the egg wasn’t fertilized, your body starts preparing to shed the thickened uterine lining during your next period. If it was fertilized, your body starts laying the groundwork for a growing pregnancy.

Is ovulation the same each month?

Ovulation is controlled by a complex balance of hormonal changes. Any differences in how that balance plays out can result in changes in ovulation.

That means that ovulation can vary each month. From cycle to cycle, you might not ovulate on the same cycle day and your body’s signs of ovulation may vary. If you have irregular cycles, you may experience more irregularity in ovulation.

Even the way ovulation happens—or doesn’t happen—can change.

Usually, for example, just one egg is released during ovulation. In a phenomenon known as hyperovulation, however, multiple eggs can mature and leave the ovaries at once. This is perfectly safe, and you may not even know it happened. If you get pregnant in a cycle where you experience hyperovulation, you may have fraternal twins.

It’s also possible for your body to skip ovulation from time to time, in what’s called an “anovulatory cycle.” Sometimes, this happens randomly. Sometimes, it could be the result of an underlying reproductive health condition like polycystic ovary syndrome (PCOS).

When do you ovulate?

Typically, ovulation occurs somewhere around the middle of a cycle. It marks the end of the first half of your cycle (the follicular phase), and the beginning of the second half (the luteal phase). 

When exactly ovulation happens for you, though, depends on your unique cycle and hormone levels.

Regular cycles last anywhere from 21 to 35 days. If your cycles generally last around 30 days, you might expect to ovulate around day 15 of your cycle. If your cycle is usually 22 days, ovulation may happen around day 11.

How can you find when you ovulate? Certain hormones provide the answer. Rising estrogen, for example, is an indication that your body is preparing for ovulation. When LH hits its peak, that’s your signal that it’s almost time: ovulation occurs around 10 to 12 hours after the LH surge. Rising progesterone then confirms that you ovulated. 

How long does ovulation last?

Although the time leading up to ovulation starts in the early follicular phase and takes a couple weeks, ovulation itself is a fairly short moment in time.

Ovulation starts when your ovaries release an egg and ends when that egg is no longer viable. 

Remember: the egg is only viable for 12 to 24 hours. That means that ovulation lasts only about a half a day to a day.

Does ovulation mean you’re fertile?

Yes—when you’re ovulating, you’re fertile.

In fact, ovulation is crucial for fertility: you need to ovulate in order to conceive, since ovulation provides the egg that can become a pregnancy (if it gets fertilized by sperm).

But you’re not just fertile in the moment of ovulation. You’re also fertile in the days leading up to ovulation. 

Do you have to have sex during ovulation to get pregnant?

Ovulation is short, but the good news is you have more than one day each month to conceive. This is because you don’t actually have to have sex during ovulation to get pregnant. 

The window of time to conceive each month is known as your fertile window, and it’s around six days long. Why six days? Because sperm can survive in the reproductive tract for up to five days post-ejaculation, and the egg released during ovulation is viable for up to one day.

That means that you have around one week each cycle to get pregnant. If you have sex at any point during the five days leading up to ovulation or the one day of ovulation, you just may conceive.

How to tell if you’re ovulating

You can tell you're ovulation through physical signs and changes in your hormone levels.

Signs of ovulation 

All throughout the reproductive period of your life (up until you’re in menopause and don’t ovulate anymore), your body may send you certain physical signs to indicate that you’re ovulating.

Many different life stages share the same signs of ovulation, whether you recently stopped birth control, you’re trying to conceive, you’re breastfeeding, or you’re in perimenopause.

Signs of ovulation include:

• “Egg-white” cervical mucus
• Elevated basal body temperature (BBT)
• Mild cramping in the pelvis or abdomen
• Breast tenderness
• Changes in cervix and cervical position
• Increased sex drive
• Mood changes
• Bloating
• Ovulation bleeding

Why should you track your ovulation

Monitoring physical signs of ovulation gives you a good starting point for understanding whether you’re ovulating, but you may want to go further.

For a greater level of certainty, you can measure and track hormone fluctuations to capture the specific changes that indicate ovulation. Tools like ovulation predictor kits or at-home fertility tests can help.

Some ovulation predictor kits, however, don’t measure enough hormones to truly indicate ovulation, or they measure hormones against “standard” levels. 

The Oova at-home fertility kit, on the other hand, measures your individual estrogen, LH, and progesterone levels to give you daily, quantitative data about your unique cycle. Plus, the Oova algorithm learns your cycle to provide accurate predictions of when you’ll ovulate.

There are lots of different scenarios where tracking your ovulation is useful. Here are just a few: 

• You’re trying to conceive: Tracking ovulation to find your fertile window will tell you when, exactly, you should have sex to conceive.
• You’re trying to conceive during perimenopause: Getting pregnant during perimenopause is possible, but can be more difficult. Tracking ovulation is key to optimizing your chances of conceiving each cycle.
• You want to avoid pregnancy: Remember, you can get pregnant from unprotected sex in the days leading up to ovulation. If you want to avoid pregnancy, make sure to use protection during your entire fertile window.
• You want to cycle sync your workouts: Monthly fluctuations in estrogen and progesterone can impact how you feel while working out. Ovulation may give you a burst of energy perfect for exercises like endurance training and cardio.
• You want to know more about your reproductive health: Measuring your hormones to track ovulation can help you better understand your cycle, your body, and your reproductive health. 

What is ovulation? The bottom line

Ovulation is the time each month, around the middle of your cycle, when your ovaries release a mature egg. If that egg is fertilized by sperm, you may become pregnant.

You’re fertile during ovulation and throughout your fertile window. That means you don’t have to have sex during ovulation to get pregnant in a given cycle—which is good news for those trying to conceive, since ovulation is only about a half a day to day long.

Ovulation is triggered by changes in key hormones like estrogen and LH. Tracking these changes with at-home fertility kits can help you pinpoint exactly when you ovulate. Physical signs of ovulation, like changes to cervical mucus or elevated BBT, can also clue you in.

Whether you’re trying to conceive, interested in cycle syncing, or just curious, tracking your ovulation can help you better understand your body, your cycle, and your reproductive health.

Frequently Asked Questions About Ovulation

What is ovulation in simple terms?

Ovulation is when your ovary releases a mature egg each month. The egg travels down the fallopian tube and can be fertilized by sperm for 12-24 hours. If fertilized, it becomes a pregnancy. If not, it disintegrates and you get your period about 2 weeks later.

When does ovulation occur in your cycle?

Ovulation typically occurs around the middle of your menstrual cycle. In a 28-day cycle, this is usually day 14. However, cycle length varies—ovulation can happen anywhere from day 11 to day 21 depending on your unique cycle length and hormone patterns.

How do you know if you're ovulating?

Signs of ovulation include clear, stretchy "egg-white" cervical mucus, mild pelvic cramping, breast tenderness, increased sex drive, and a slight rise in basal body temperature. The most accurate way to confirm ovulation is tracking hormone levels, specifically the LH surge followed by rising progesterone.

Can you get pregnant when you're not ovulating?

No, you cannot get pregnant without ovulation because there's no egg available for fertilization. However, you can get pregnant from sex that happens before ovulation since sperm can survive up to 5 days waiting for the egg to be released.

How long does ovulation last?

Ovulation itself lasts only 12-24 hours the time the egg remains viable after being released. However, your fertile window is about 6 days long (5 days before ovulation plus ovulation day) because sperm can survive in the reproductive tract for up to 5 days.

What happens if you don't ovulate?

Not ovulating (called an anovulatory cycle) means you cannot get pregnant that month. Occasional anovulatory cycles are normal, but frequent lack of ovulation may indicate conditions like PCOS, thyroid issues, or perimenopause, and should be discussed with a healthcare provider.

How long should I try to conceive before seeing a doctor?

If you're under 35, healthcare providers typically recommend seeking medical evaluation after 12 months of regular unprotected intercourse without conception. However, if you're 35 or older, it's advisable to consult a fertility specialist after just six months of trying, since fertility declines more rapidly in the mid to late 30s. If you have irregular cycles, a history of miscarriages, known reproductive health conditions like PCOS or endometriosis, or other concerning symptoms, you may want to see a specialist sooner.

Can I ovulate more than once in a cycle?

While you can't ovulate on separate days within the same cycle, your body can release multiple eggs at the same time during a single ovulation event, a phenomenon called hyperovulation. When this occurs, both eggs are released within a 24-hour window on ovulation day. Hyperovulation can result in fraternal twins if both eggs are fertilized by different sperm. Factors like age over 35, genetics, and recent discontinuation of hormonal birth control can increase the likelihood of hyperovulation.

What affects my chances of getting pregnant each cycle?

For couples with no fertility issues, the overall rate of conception in any given month is about 25%. Nearly 80% of couples become pregnant within the first six months of trying. The highest pregnancy rates occur when couples have intercourse during the one to two days immediately before ovulation, within the six-day fertile window that ends on ovulation day. Beyond timing, factors like age, overall health, lifestyle choices, and underlying reproductive conditions can all influence your monthly conception chances.