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Articles / When do you ovulate? Methods to determine the most fertile days of your cycle

When do you ovulate? Methods to determine the most fertile days of your cycle

When do you ovulate? Before answering this question: is it even important to know when you ovulate? Is such knowledge necessary? In certain circumstances, while trying to get pregnant, it is. There are many ways to determine your fertile days. They vary in level of complexity, reliability and cost. Here are some advantages, disadvantages and guidelines for each method.

Isn’t it enough to have intercourse every two to three days during the whole cycle to make sure that sooner or later conception happens? Regular intercourse in most healthy couples will eventually result in pregnancy. About 20% of couples will get pregnant each month. Why then do so many couples try to determine their fertile days?

The most basic reason is because most couples want to conceive sooner rather than later. They don’t want to wait for a few, or even several months. For others, being aware of their body increases their sense of safety and the quality of their conception experience. There are also couples for whom knowing about their fertile days is the only way to conceive. Often, for medical reasons, such as poor quality or insufficient quantity of fertile mucus, they need to plan intercourse as close to ovulation as possible.

Determining ovulation, the point when a dominant follicle releases a mature egg cell into the fallopian tube, can be difficult in many cases. Contrary to common belief, ovulation does not always occur around the fourteenth day of the cycle, nor does it occur in the middle of the cycle. Ovulation may occur as early as on the tenth day of the cycle, but also as late as the twenty-first day or even later. There are many couples which have intercourse around the fourteenth day of the cycle, but are unsuccessful in conceiving. Their stress grows from cycle to cycle, while they’re unaware that they’re bypassing their most fertile days. Therefore, if you are trying to have a baby, you should have sex regularly throughout the whole cycle, or take the time to broaden your knowledge about your actual date of ovulation.

So when do you ovulate? Fortunately, there are many ways to find out. They vary in their level of complexity, reliability and cost.

women charting her fertile days

 The simplest method is to calculate the ovulation date based on the average length of your cycle. This method involves estimating when ovulation may happen.

To calculate when you can expect to ovulate, you need to know the average length of your cycle for the last several months. A cycle should be calculated starting from the first day of menstruation up until the last day before the next menstruation. Once you know the average length of your cycle, determine when your next menstruation will start (mark it in your calendar), and subtract 12 days, and then another four days. Your ovulation may occur in the course of the following five days. For example, if your cycles last on average 31 days, then: 31 - 12 = 19, and 19 - 4 = 15. Your ovulation may occur between the fifteenth and the nineteenth days of the cycle.

At OvuFriend, you will find these calculations under the chart, marked as "expected date of next menstruation".


  •  Low level of difficulty.
  •  It’s free.


  • This method is not complicated, but also not very reliable. It does not consider the fact that every woman’s body is different, and the menstrual cycle is dynamic and variable.
  • It does not give any indications whether ovulation has occured.
  • This method does not work with irregular cycles, because it’s difficult to determine the average length of these cycles (the discrepancy between the length of each cycle is too wide).

Tip: If, at the moment, this is the only method you want to use, it’s certainly better than being completely unaware of when your fertile days may happen. However, if you are looking for more accurate methods of determining fertile days, acquaint yourself with the much more reliable methods below.

 Observing your body is a method that involves tracking changes in cervical mucus (vaginal discharge) and/or the cervix, that occur throughout the duration of the cycle due to the hormones inside the woman’s body. On the infertile days of your cycle, there will be little mucus and it will be sticky, whitish and rather difficult to notice. As you get closer to ovulation, the quantity of mucus will increase, and it will become flexible and transparent. The inside of your vagina will feel moist and slippery. The appearance of fertile mucus indicates impending ovulation. Similarly, hormones affect the position, texture and degree of openness of your cervix. You may observe the mucus and the cervix at the same time or, if you don’t feel comfortable observing both, focus on observing only one (e.g. the cervical mucus).


  • Low level of difficulty.
  • It’s free.
  • Doesn’t take much time.
  • If done correctly, it will provide you with good results to help determine your potentially fertile days.


  • Fertile mucus can be easily confused with mucus occurring during arousal or with sperm.
  • Some medications may disrupt mucus production.
  • This method does not indicate the occurrence of ovulation, it only informs you that ovulation is coming.
  • Some women produce only a small amount of mucus, which may make observation difficult.
  • Many women do not feel comfortable checking their cervix.
  • It requires practice to learn to recognize the changes occurring in the mucus and the cervix.

Tip: It is best to combine this method with the thermal method (measurement of basal body temperature). This allows you not only to get the information that ovulation is coming, but also to confirm that it has actually happened.

Read about and learn the rules for checking your mucus and cervix. Start to have intercourse regularly as soon as you notice the fertile mucus.

 The thermal method (charting your basal body temperature) involves taking your basal body temperature daily (orally or vaginally). Always take your temperature at the same time of the day - in the morning, just after waking up and before any activity.  Are you wondering how your body temperature will help determine your date of ovulation? Although you don’t feel it, shortly after ovulation occurs your body temperature rises and remains elevated up until the end of your cycle (until your next menstruation). This is due to the presence of progesterone, the hormone released after ovulation, which increases the body’s temperature. If ovulation does not occur, the body temperature does not rise, and the cycle is called anovulatory, meaning ovulation did not occur.


  • One of the few methods to actually indicate the occurrence of ovulation (most methods only inform you that ovulation is coming).
  • In most cases, the correct use (both by taking your temperature, charting and correctly interpreting the cycle) renders it a very reliable method of determining your date of ovulation.
  • Very low cost, if any.
  • It provides additional information about your cycle and fertility, and thus allows you to detect possible anomalies early on.
  • It may also be used by women who have irregular cycles, and who tried the other methods without success.


  • Requires daily, regular use.
  • May be too complicated for individual interpretation.
  • May require a few of months of practice in order to learn the specification of the cycles.

Tip: The efficiency of this method depends mostly on the correct interpretation of the temperatures taken. That’s why it’s a good idea to use OvuFriend, which will interpret the data entered for you, determine the most probable date of ovulation, inform you about your fertile days and run an analysis of the cycle, paying attention to its deviations and anomalies.

It is recommended to combine the thermal method with other methods, like the observation of mucus or ovulation tests; then, it can be a part of a comprehensive method of analysis of your own fertility.

 Urine ovulation predictors (ovulation tests and ovulation monitors) entails carrying out urine ovulation predictors a few days prior to the expected day of ovulation. The ovulation tests recognize a higher level of LH (luteinizing hormone) in the woman's urine, indicating an impending ovulation. Ovulation monitors are also available on the market. These examine not only the level of LH, but also that of estrogen. Once you get a positive result (read the leaflet carefully to learn how to recognize a positive result), there is a high probability that ovulation will soon occur. Remember that urine ovulation predictors don’t confirm that ovulation has occurred. It may happen that the body is preparing for ovulation, LH and estrogen levels have increased, but ovulation does not occur (e.g. due to illness or stress).


  • The ovulation predictors are carried out for only a few days in the cycle, not for its entirety.
  • You don’t have to wait very long for the results, as the tests indicate fertile days even the first time you use them.


  • The ovulation predictors do not confirm the occurrence of ovulation. They only inform you about impending ovulation.
  • The ovulation predictors are costly. With long and irregular cycles, the cost may be a lot higher, because then you have to take an accordingly higher number of tests and one box may not be enough.
  • If the peak value of LH (the value recognized by ovulation predictors) in your body lasts fewer than ten hours, the test may give a negative result, even though ovulation may still occur.

Tip: First, carefully read the test instructions. Also, remember that if the length of your luteal phase is atypical, you should start taking the ovulation tests earlier or later than indicated in the instructions (the manufacturer indicates the date you should start the test based on an average length of the luteal phase). If you keep the OvuFriend ovulation calendar, it’s best to start using the ovulation tests when you approach the expected date of ovulation on the chart (called statistic, marked in green under the chart). It’s a good idea to combine these tests with taking your basal body temperature and observation of the body, because only then can you be sure that ovulation has actually occurred.

 USG monitoring of follicular growth - While doing an ultrasound for a few consecutive days during the first half of your cycle, a doctor observes the changes in your body (the amount and the rate of growth of the Graafian follicles and the endometrial development), and checks if ovulation occurs. Usually it takes about three, sometimes four, visits at the doctor's office, two or three days apart.


  • The most reliable method for determining the date of ovulation.
  • It can provide you with additional information about your fertility and immediately pick up on any irregularities.
  • When a doctor finds some anomalies, appropriate steps are taken.


  • A costly method if your insurance does not cover infertility treatment.
  • Requires several visits at the doctor's office (time consuming).

Tip: Because of the high cost involved, most women try to determine the date of ovulation themselves when they first start trying to have a baby. If, however, you have been trying to conceive for about a year (or six months if you’re over 35) and you keep failing to get pregnant, you should make an appointment with a doctor in order to check whether everything is in order. It’s a good idea to undergo USG monitoring of follicular growth with a doctor who specializes in fertility issues. Such a doctor will be able to provide you with the best course of treatment if he or she happens to find some anomalies.

 The last method, or, to be precise, a supplement to the above methods of determining your fertile days, is to watch out for subjective sensations of impending ovulation. About 20% of women experience symptoms of impending ovulation, repeating from cycle to cycle. The most common of these symptoms are:

  • Pain or stinging in the ovaries.
  • Staining.
  • Increased libido.
  • Sensitive breasts.
  • Feeling of fullness in the lower abdomen.

Some women recognize their own specific symptoms, which recur regularly during the days around ovulation. It is, therefore, a good idea to listen to your body, and note all the important signals it sends you. They can provide additional information to help determine the most fertile days in your cycle.

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