Fertile days: what are they and how are they calculated?

In this article we will explain which are the fertile days of the cycle, how to calculate them and how to recognize them to increase your chances of conceiving.

Are you and your partner trying for a baby? If the answer is yes, it could be very useful to know what your fertile days are , which are the best times to have intercourse to get pregnant .

If you’re eager to know them, you can use our fertile window calculator before reading this article .

All you need to do is select the date of your last period and the average length of your cycle , i.e. how many days pass on average between one period and the next.

For the more experienced, who are already monitoring their menstrual cycle, it is also possible to enter the duration of the luteal phase , to obtain a more accurate calculation of fertile days .

What are the fertile days of the cycle?

As we know, for conception to occur, the fateful encounter between a male sperm and a female egg must take place .

However, while a healthy man produces millions of new sperm every day, a healthy adult woman releases only one egg every 21-35 days, which remains alive for approximately 12-24 hours .

With such a small window of fertility , it might seem nearly impossible to get pregnant. Fortunately, sperm cells can live for 3 to 5 days inside the female body.

Consequently, a woman’s fertile period includes the 5 days preceding ovulation, the day itself and the day after.

During this time frame, however, the likelihood of getting pregnant is highest on the day of ovulation and the two days before it .

How to calculate ovulation and fertile days

To calculate when your cycle is fertile, you need to predict when you will ovulate . To do this, you need to know 3 pieces of information:

1.     the date of the last menstrual period (mandatory) , i.e. the day on which the last menstrual flow began;

2.     the average length of the cycle (mandatory) , i.e. how many days usually pass between one period and the next. If the cycle is regular, the duration will always be the same and the ovulation calculation will give a more reliable result.

3.     the duration of the luteal phase (optional) , i.e. how much time passes between ovulation and the onset of menstruation.

This phase is constant in every woman and usually lasts 12-14 days . However, some women have a shorter or longer luteal phase , which is still considered normal if it is between 11 and 17 days .

If the length of the luteal phase is unknown , the Ogino-Knaus method will assume the 14-day mean value.

With this data, it is possible to calculate when ovulation is expected.

• How to calculate ovulation

To figure out when you’ll ovulate, simply subtract your luteal phase length from the date you expect your next period .

Example

If your cycle averages 30 days and you had your period on May 1st, your next period will start on May 31st. By subtracting 14 days, your expected ovulation date is May 17 (31-14=17).

However, if you know your luteal phase is 16 days long, you will ovulate on May 15th (31-16=15).

• How to calculate your fertile days

Even when you have a regular cycle, ovulation can come earlier or later due to various factors, such as stress, illness, dietary changes. The ovulation calculation, therefore, is only a rough estimate.

For this reason, the Ogino-Knaus method considers the period from 2 days before to 2 days after the presumed ovulation as the window of maximum fertility .

Furthermore, the 3 days before and after the period of maximum fertility are also considered fertile days in the calculation .

Example

If the expected date for ovulation is May 15, we will have:

• very fertile days = 13 to 17 May
• fertile days = from 10 to 12 May and 18 May
• infertile days = all others in the cycle

Symptoms of ovulation

Calculating your fertile days can help you get pregnant more easily , but it’s just a starting point.

In fact, the best way to pinpoint your fertile window is to learn about ovulation symptoms .

Here are some:

• increase in basal temperature
• egg white cervical mucus
• softer and more open cervix
• breast tension
• mild cramps or twinges in the abdomen
• light bleeding ( spotting )
• increased sexual desire

In addition, using ovulation tests may also help to get pregnant more quickly  . However, a positive result does not mean that ovulation will occur 100%: these sticks, in fact, are not able to recognize an anovulatory cycle .

Tips to help conceive 

• Before even starting the search, consult your trusted gynecologist and have the necessary tests prescribed.

• Start taking a folic acid supplement .

• Eliminate unhealthy habits, such as smoking and alcohol intake , and follow a balanced diet .

• Get regular physical activity .

• Try to get enough sleep and reduce stress .

• Limit caffeine to no more than 200 milligrams per day.

• Try to have frequent intercourse , preferably every other day during the fertile period.

• Your sexual position does not affect your chances of getting pregnant.