When Do You Ovulate?

When Do You Ovulate?
Ovulation. Photo Courtesy of Science Picture Co/Getty Images

In order to successfully be able to know the answer to the question, there are a few issues that you must first take into consideration. First and foremost is knowing exactly what happens when you ovulate, how often it occurs, and what ovulation means.

Many women confuse ovulation with having their periods, with PMS, and with conception, so it is important to know your facts. Additionally, the reason why you want to know when you ovulate may factor into the type of information you may be looking for.

Do you need to know your ovulation date as part of a natural family-planning method to avoid pregnancy, or are you trying to maximize your opportunity to get pregnant?

The Basics

To understand when you ovulate, let’s start with some basic definitions:

  • Ovulation: The time a mature egg (possibly more) is released from your ovary. At this time, an egg is vulnerable to being fertilized by a sperm, thereby resulting in conception.​
  • Menstrual Period: Marks the first day of your next cycle. Your period occurs as a result of the hormonal changes that take place when an egg has been released, not fertilized and dies. These hormones indicate that no pregnancy has occurred, so the uterus begins to shed its lining to prepare for your next ovulation day.

Who Ovulates?

Having a menstrual period is usually an indication that you have ovulated. Ovulation typically occurs in the middle of your menstrual cycle.

So when you have a period, this means that you are beginning your next cycle and have likely ovulated the cycle before. This is one area where women get into trouble. Many women who have not had a period in a while (do to stress, miscarriage, breastfeeding, having given birth, etc.) use their periods to determine that they are fertile (ovulating) again.

However, if you had been having unprotected sex prior to this time, you could be at risk for pregnancy since your ovulation will have taken place before your period resumes.

If you have excessive monthly bleeding, infertility issues or irregular menstrual cycles, you may or may not be ovulating. If this applies to you, it is important that you try to determine if and when you ovulate. You may need to seek the assistance of a doctor and have blood tests to confirm that you are ovulating.

Most women’s menstrual cycles last 28 to 35 days. There seems to be relatively little cycle variability among women between the ages of 20 and 40. However, a woman may experience considerable cycle variability during the first five to seven years after she first gets her period as well as during the last 10 years before menopause (the stopping of your cycle). Typically, menstrual-cycle length peaks at about age 25 to 30 years and then slowly drops, which is why women in their 40s may have somewhat shorter cycles.

Women Using Hormonal Contraception

Listen up, ladies, because, in my experience, it appears many of you do not realize what I am about to tell you. If you are reliably using a hormonal contraceptive (especially a combination method that contains both estrogen and progestin)... are you listening? You do not ovulate.

The hormones in these contraceptives suppress ovulation from occurring, which is what makes them effective birth control methods. Stop the egg from being released = no egg = nothing for the sperm to fertilize = no baby.

So, if you are using these methods, please do not try to track, either by temperature, charts, kits, etc., your ovulation patterns... since there are none! You do not have "more fertile days" in the middle of the month. You are no more at risk for pregnancy than any other day of the month. For those of you who use hormonal methods, the risk factors for contraception failure have to do with if you forget to take pills, change your patch or if your NuvaRing falls out, etc. With these methods, you need to make sure that there are enough hormones in your body to suppress your ovulation. If you miss too many pills (especially during the first week of a pack or at the end of Week 3, where you need to have enough hormone built up to protect you against the hormone-free Week 4), you may be at risk for ovulating.

What Happens Up to and After Ovulation?

Your normal menstrual cycle is a synchronized cycle of hormonal changes that produces a mature egg (oocyte) to be released. In order to have the most accurate information and learn what is exactly going on in your body, I consulted an article on UpToDate - a trusted electronic reference used by many doctors and patients. According to this excerpt from UpToDate:

"The first day of menses represents the first day of the cycle (Day 1). The cycle is then divided into two phases: follicular and luteal. The follicular phase begins with the onset of menses and ends on the day of the luteinizing hormone (LH) surge. The luteal phase begins on the day of the LH surge and ends at the onset of the next menses.

Follicular Phase: The early follicular phase in humans is the time when the ovary is the least hormonally active, resulting in low serum estradiol and progesterone concentrations. Release from the negative feedback effects of estradiol, progesterone, results in a late luteal/early follicular phase increase in gonadotropin-releasing hormone (GnRH) and a subsequent increase in serum follicle-stimulating hormone (FSH) concentrations. The modest increase in FSH secretion in the early follicular phase gradually stimulates folliculogenesis and estradiol production. By the late follicular phase, a single dominant follicle has been selected. The dominant follicle increases in size by about 2 mm per day until a mature size of 20 to 26 mm is reached. Rising serum estradiol concentrations result in gradual thickening of the uterine endometrium and an increase in the amount and "stringiness" of the cervical mucus. Many women are able to detect this change in mucus character.

Luteal Phase: Serum estradiol concentrations continue to rise until they reach a peak approximately one day before ovulation. Then, a unique neuroendocrine phenomenon occurs: the mid-cycle surge, resulting in a 10-fold increase in serum LH concentrations and a smaller rise in serum FSH concentrations. The oocyte is released from the follicle at the surface of the ovary approximately 36 hours after the LH surge. It then travels down the fallopian tube to the uterine cavity. A gradual decrease in LH secretion results in a gradual fall in progesterone and estradiol production by the corpus luteum in the absence of a fertilized oocyte. If, however, the oocyte becomes fertilized, it implants in the endometrium several days after ovulation. The decline in estradiol and progesterone release from the resolving corpus luteum results sequentially in the loss of endometrial blood supply, endometrial sloughing, and the onset of menses approximately 14 days after the LH surge."

So, in lay terms, each month a series of events occur within a woman’s body. The follicular phase starts with the first day of your period (which is considered Day 1 of your cycle). Low estrogen and progesterone levels help your brain produce the gonadotropin-releasing hormone (GnRH). The GnRH will then activate the pituitary gland to release the follicle-stimulating hormone (FSH). FSH triggers your follicle to grow, and as it does, it causes the production of more estrogen. The follicle grows, your uterine walls become thicker (preparing for possible implantation) and your cervical mucus becomes thinner and stretchier. Your estrogen levels increase over the next 10 days and peak usually one day before ovulation (in a 28-day cycle, this typically occurs on Day 13). This estrogen peak initiates the luteinizing hormone (LH) surge.

After this surge occurs, you are now in the luteal phase of your cycle. The increased levels of LH cue the ovarian follicle, and ovulation occurs about 24 to 36 hours later. Once the egg is released, it leaves behind the corpus luteum (the empty follicle). Progesterone released from the corpus luteum after ovulation will cause a rise in basal body temperature (your temperature when you're fully at rest) of 0.5°F. If the egg is not fertilized, your LH levels begin to decline and cause the corpus luteum to begin to shrink and produce less progesterone and estrogen. These low levels of hormones cause body temperature to lower, signal your brain to start the whole cycle over again and trigger the uterine lining to shed - thus begins your next period.

This first half of your cycle (the follicular stage) can differ greatly for each woman, usually lasting between 14 and 21 days. The second half of your cycle (the luteal phase) typically has a more precise timeline, beginning on the day you ovulate and usually lasting 14 days. It usually does not vary by more than a day in each individual.

Ovulation Day

In sum, to determine when you do ovulate, you need to count 15 days back from the first day of your period. This is most likely when your LH surge has occurred. Then you can assume that you would have ovulated 1 1/2 days (24 to 36 hours) later. For a 28-day cycle, this would be sometime on Day 14 or 15 (depending on the time the LH surge occurs). Remember: To calculate upcoming ovulation, you need to:

  • Count back from Day 1 of your cycle.
  • Have reliable cycles that last the same number of days each time.
  • Realize that this is not an exact science - many factors, such as stress, illness or disruption of normal routines, can affect/hinder the hormone production required for ovulation to occur.
  • Understand that not all women will ovulate the same time every month.
  • Know that not all women ovulate - especially women who have short menstrual cycles. Menstrual cycles that last 25 to 35 days are generally considered ovulatory.

Want to learn more? See UpToDate's topic, "Physiology of the normal menstrual cycle," for additional in-depth medical information.


Welt, Corrine K. "Physiology of the normal menstrual cycle." UpToDate. Accessed: February 2012.

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