Fertile Period Calculator

How to calculate the fertile period using the calculator?

To know when your fertile period is, just put the date of the first day of your last period above. Also inform the number of days in your menstrual cycle and how many days you usually have your period. Our calculator will show you a calendar with your chances of getting pregnant. It is possible to see the days when you are most likely to become pregnant based on the data provided. If you want to know more details about how this calculation is done see our post that explains how to know the fertile period and what are the expected symptoms . See below for an example of how the result of our calculator:

Calendar with Fertility Period Table

Example of the calendar generated by our calculator. The days of menstruation (drops of blood), the date of ovulation (egg). The best days to have sex in an attempt to conceive are marked with hearts.

In the results of our calculator it is also possible to see a table with the next six menstrual cycles. This helps, for example, to plan a trip or other appointment. Allowing you to optimize your chances of getting pregnant, even if your cycle is not 28 days.

But be careful, if you have an irregular cycle the calculator and the calendar may be less accurate. In this case it is important for the woman to make an appointment with her gynecologist. Some tests can help you find out when you ovulate. The ovulation control exam for example will look at your ovary to monitor it during the menstrual cycle. This allows you to tell when the egg is about to be released, at which point ovulation occurs. The menstrual cycle can vary with seasonal changes and according to age.

What is the fertile period?

The fertile period is the time of the menstrual cycle when there is the greatest chance of pregnancy. In a normal 28-day cycle, ovulation is expected to occur 14 days after the start of menstruation. Some women may experience pain on the day of ovulation. The body temperature can also rise a little, around 0.5 ºC. Also a little bit of pain can be felt when the ovary releases the egg. Often the woman may notice a mucous discharge on the first day after ovulation, similar to an egg white. Libido (sexual desire) can also increase during the fertile period.

Fertile days are usually 6 days . The period ranges from about 5 days before ovulation to one day after ovulation. However the greatest chance of pregnancy is about one to two days before ovulation until the day of ovulation.

It is also important to inform that the fact that you are not in the fertile period does not mean that you have no chance of getting pregnant. Yes, it is possible to estimate the date of ovulation! But the tablet is not an effective contraceptive method. Without complementary exams (such as ultrasound or hormonal dosages) it is not possible to be sure. Therefore, our fertility table should not be used as a contraceptive method .

Understanding how the Fertile Period is calculated

To calculate the fertile period we first need to understand the menstrual cycle. It can be divided into two phases. The first, called the proliferative phase, is characterized by the secretion of the hormone estrogen . The second phase, called secretory, is characterized by the hormone progesterone . Between these two phases, ovulation occurs, which is basically controlled by these hormones.

While the first phase has a variable duration, the second phase is quite constant, with a duration of 2 weeks. So ovulation occurs about 2 weeks before the date when you are expecting your next period. Got confused? Let’s see some examples:

Example 1: 28-day menstrual cycle

First phase (variable) has 14 days (counted from the first day of menstruation)
Ovulation on the 14th day of the cycle
Second phase (constant) has 14 more days
Menstruation comes every 28 days (14 days from first phase + 14 days of the second phase)

Example 2: 24-day menstrual cycle

First phase (variable) has 10 days (counted from the first day of menstruation)
Ovulation on the 10th day of the cycle
Second phase (constant) has 14 more days
Menstruation comes every 24 days (10 days from first phase + 14 days of the second phase)

Example 3: 35-day menstrual cycle

First phase (variable) has 21 days (counted from the first day of menstruation)
Ovulation on the 21st day of the cycle
Second phase (constant) has 14 more days
Menstruation comes every 35 days (21 days from first phase + 14 days of the second phase)

Of course, if you have an irregular cycle it is often difficult to determine clearly what your fertile period is.

How many days after menstruation is the fertile period?

To answer that question you need to understand 2 things. The first is that the egg can be fertilized up to approximately 24 hours after ovulation. The second is that the sperm is able to survive for up to 5 days. Therefore pregnancy is possible for some women if you have intercourse from 5 days before ovulation until the day after ovulation.

What is the relationship between the fertile period and ovulation?
To know your fertile period, if you have regular cycles, just determine the probable day of ovulation. Five days before and until one day after this date will be the period when you can get pregnant. For example, if your cycle is 28 days old and you had your period on 5/1, ovulation will be around 15 May. Then the fertile period is approximately from the 10th to the 16th (5 days before to one day after ovulation).

What are the symptoms of the fertile period?

There is no symptom of the fertile period , but what some women notice are the symptoms of ovulation . If you have the symptoms below it could mean that you are ovulating. This day or the next day there is a good chance that you will become pregnant if you have unprotected sex. These are your fertile days and the main signs to be able to identify your ovulation are:

• Increase of basal body temperature by about 0.3ºC.
• Vaginal discharge, light, clear, transparent and thin. With a more slippery consistency and with the appearance of mucus, similar to that of egg white.
• Pain in the lower abdomen, on the side where ovulation is taking place. This type of pain is called Mittelschmerz (from the German “middle pain”), it can appear suddenly and usually improves after a few hours. It occurs at the moment the eggs are released.
• Increased sexual desire.
• Discrete vaginal blood loss.
• The vulva or vagina may appear swollen.
• Increased sensitivity in the breasts.
• Smell becomes more sensitive (sometimes, the taste too).
• Sensation of gas in the belly.

There are still some pharmacy tests on the market that help you know if you are ovulating and even ultrasound tests that can help, such as ovulation control . Talk to your doctor if you need help to know when to ovulate or what your fertile period is. If you are trying to get pregnant in this cycle be sure to read our tips on sexual positions that increase the chance of getting pregnant .

What is the percentage of chance of becoming pregnant in the fertile period?

The chance of becoming pregnant during the fertile period varies depending on the day you have intercourse. A day or two before you ovulate is your best chance of getting pregnant on that cycle. See the chart below where on the X-axis there is the day in relation to ovulation (day 0) and on the Y-axis the chance of becoming pregnant.

Chance to Get Pregnant in the Fertile Period

Probability of Pregnancy According to the Date of Coitus / Ovulation. The day of ovulation is day 0 (zero). Adapted from Dunson et. al, Assessing human fertility using several markers of ovulation. Statistics in Medicine, 2001.

What is the chance of getting pregnant after menstruation?

Right after menstruation the chance of getting pregnant is very low because the uterus is not prepared to receive the fertilized egg. However, regardless of the phase of the cycle, we can never be 100% sure of the ovulation date. Therefore, the table method (having a relationship only on non-fertile days) is not reliable. If you are looking for a contraceptive method, see your doctor.

Why use a calculator to determine your fertility?

If you are taking a while to get pregnant knowing your fertile day can be a good help. Although your body gives you a lot of clues that you may be ovulating, keeping track of your menstrual cycles and being able to estimate your fertile period increases your chances of getting pregnant.

Although on average a couple conceives after about 5 or 6 months of trying, people who know how to determine their ovulation and maintain unprotected relationships during the fertile period increase their chances of getting pregnant!