Ovulation is the moment when a mature egg is released from an ovary into a fallopian tube, where it can potentially be fertilized by sperm. It typically happens around day 14 of a 28-day menstrual cycle, though the exact timing varies from person to person and even cycle to cycle. Understanding when ovulation occurs is essential whether you’re trying to conceive or simply trying to understand your body’s monthly rhythm.
How Ovulation Works
Ovulation is the result of a carefully timed hormonal sequence that begins weeks before the egg is actually released. Starting around day 6 of your menstrual cycle, a hormone called FSH (follicle-stimulating hormone) causes several small fluid-filled sacs, called follicles, to start developing on one of your ovaries. Each follicle contains an immature egg. Over the next week or so, one follicle outpaces the others and becomes the dominant one, while the rest stop growing.
As the dominant follicle matures, it produces rising levels of estrogen. That rising estrogen signals your pituitary gland (a small gland at the base of your brain) to release a sudden burst of luteinizing hormone, or LH. This LH surge is the direct trigger for ovulation. About 36 to 40 hours after LH levels spike in the blood, the mature follicle ruptures and releases its egg. The egg then enters the fallopian tube and begins its journey toward the uterus.
When Ovulation Happens in Your Cycle
In a textbook 28-day cycle, ovulation occurs around day 14. But most people don’t have a textbook cycle. Cycle lengths between 21 and 35 days are considered normal, and ovulation timing shifts accordingly. The key thing to understand is that the second half of your cycle, from ovulation to the start of your next period, is relatively fixed at about 14 days. It’s the first half that varies. So if you have a 32-day cycle, you likely ovulate around day 18, not day 14.
This also means that if your cycle length fluctuates from month to month, ovulation day shifts too. Tracking your cycle over several months gives you a much better estimate than relying on a single number.
Your Fertile Window
Once released, an egg survives for only about 12 to 24 hours if it isn’t fertilized. Sperm, on the other hand, can survive inside the reproductive tract for 3 to 5 days. This mismatch is what creates the “fertile window,” a span of roughly six days: the five days before ovulation plus the day of ovulation itself.
Not all days within that window carry equal odds. The highest chance of conception comes from having sex one or two days before ovulation. The probability of pregnancy two days before ovulation is around 26%, compared to just 1% the day after ovulation. By the time the egg has been out for more than 24 hours without being fertilized, conception is essentially off the table for that cycle.
Physical Signs of Ovulation
Your body gives several signals that ovulation is approaching or has just occurred. None of these are perfectly reliable on their own, but together they can paint a useful picture.
Cervical Mucus Changes
The consistency of your cervical mucus shifts throughout your cycle. In the days after your period, mucus tends to be dry or sticky, sometimes pasty and white. As you approach ovulation, it becomes creamy and smooth. Right before and during ovulation, it turns clear, wet, and stretchy, often compared to raw egg whites. If you can stretch it between your fingers without it breaking, you’re likely in your most fertile phase. After ovulation, it returns to thick and dry.
Ovulation Pain
Some people feel a distinct twinge or cramp on one side of their lower abdomen around the time of ovulation. This is called mittelschmerz, a German word meaning “middle pain.” It can feel dull and achy like mild menstrual cramps, or it can be sharp and sudden. The pain typically lasts anywhere from a few minutes to a few hours, though it occasionally persists for a day or two. Some people experience it every month, others only occasionally, and many never notice it at all. Slight vaginal spotting can accompany it.
Basal Body Temperature
Your resting body temperature rises slightly after ovulation, typically by 0.4°F to 1°F (0.22°C to 0.56°C). The shift is small enough that you need a sensitive thermometer and consistent daily measurements taken first thing in the morning, before getting out of bed. The important caveat: the temperature rise confirms that ovulation has already happened, so it’s more useful for confirming patterns over several months than for predicting ovulation in real time.
How Ovulation Prediction Tests Work
Over-the-counter ovulation predictor kits detect the LH surge in your urine. Once the test turns positive, ovulation typically follows within 12 to 24 hours. This gives you a shorter and more actionable heads-up than waiting for a temperature shift. For the best results, start testing a few days before you expect to ovulate based on your usual cycle length. If your cycles are irregular, you may need to test over a longer window.
What Can Disrupt Ovulation
Sometimes the hormonal chain reaction that leads to ovulation doesn’t complete, and no egg is released. This is called anovulation. An occasional anovulatory cycle is normal, especially during puberty, the years approaching menopause, or after stopping hormonal birth control. Chronic anovulation, however, is a different story.
Polycystic ovary syndrome (PCOS) is the most common medical cause. It involves a hormonal imbalance that interferes with follicle development, often leaving multiple small follicles on the ovaries without any of them maturing enough to release an egg. Thyroid disorders, particularly an underactive thyroid, can also suppress ovulation, as can conditions that affect the pituitary gland or lead to elevated levels of prolactin (a hormone normally associated with breastfeeding).
Lifestyle factors play a significant role too. Being significantly underweight, especially from restrictive eating or excessive exercise, can cause the body to shut down ovulation as a kind of self-protective response. Obesity can disrupt the hormonal balance needed for regular cycles. Chronic or extreme stress affects the hypothalamus, the part of your brain that kicks off the entire hormonal cascade, and can delay or prevent ovulation. Certain medications, including some anti-seizure drugs, antipsychotics, and anabolic steroids, can also interfere.
If you’re not getting a period at all, getting periods very irregularly, or tracking ovulation signs without ever seeing the expected patterns, anovulation may be the reason. It’s one of the most common and most treatable causes of difficulty conceiving.