Ovulation calculator: Calculate fertile days reliably

If you are planning to get pregnant, it is helpful to know the exact day of your ovulation. After all, fertilization can only occur on a few days of the month, as it must take place within the ovulation period. Especially if you have not yet been able to get pregnant, it is important to observe your cycle and find out when your fertile days are.

Thanks to our handy ovulation calculator, you don’t have to count for long. You can easily display the time period of your ovulation.

First day of the last menstruation:

Days (on average 28 days, if you do not exactly know how long your cycle is)


= first day of the menstruation
= probable ovulation
= rather a girl
= rather a boy
= fertile days
= highly fertile days

How does the HiPP Ovulation Calculator work?

Use our practical ovulation calculator to determine your fertile days. Within a few seconds it will provide you the possible conception days.

A woman’s menstrual cycle begins on the first day of her period. Every woman has her own  duration and course of menstrual cycle. In most cases a cycle lasts 23 – 35 days. The length of the cycle varies not only from woman to woman but can also vary from cycle to cycle. Simply enter in the ovulation calculator on which day your last menstruation began. Select the day, month and year. Also enter the length of your cycle. Then click on “Calculate now”. The displayed calendar now shows the ovulation period.


Supposing your last menstrual period started on 11 June 2020. The length of your cycle is 28 days.

Then you will see that the fertile days are in the period from 20 to 25 June 2020. This is shown in the pink fields. In our example, 23 and 24 June 2020 are the days on which you are particularly fertile. The probable date for ovulation is 24 June 2020. Around 20 June 2020, the chances of conceiving a girl are particularly good. For a boy, the chances are particularly good on 24 June 2020.

Keeping an eye on your cycle

To find out your fertile days using our ovulation calculator, you should have an overview of your menstrual periods. If you have a strong wish to have a child, it can therefore be useful to track your period with a menstruation app. Tracking also has other positive effects:

  1. It helps your gynaecologist to better assess your cycle.

  2. Tracking can be used in addition to different methods of contraception. It is not suitable as the only method of contraception.

  3. If you frequently suffer from mood swings, pimples or unexplained discomfort, this may also be related to your cycle. Tracking helps you to draw appropriate conclusions and can be helpful for further treatment or lifestyle changes.

Things worth knowing about ovulation

What is ovulation?

During ovulation, an ovarian follicle bursts open and releases the egg and nourishing cells. In order to prevent it from disappearing into the abdomen, one of the very flexible, fringed funnels (fimbriae), which are located at the end of each fallopian tube, bulges over the ovary and sucks in the egg together with the fluid.

The empty follicle retracts into the ovary and, under the influence of the luteinizing hormone (LH), it transforms into the so-called corpus luteum. The follicle takes on a yellow colour when it changes. Its main task is the production of progesterone (gestagen), which prepares the uterine lining for a possible pregnancy. In order to become pregnant, the egg cell must, of course, be fertilised by sperm.

For the control centre in the diencephalon, progesterone in the blood means that a pregnancy may already have occurred. No further ovulation can then take place.

The pill also works through this mechanism: the body is continuously supplied with synthetic gestagens that mimic a second half of the cycle or a pregnancy and thus inhibit the onset of ovulation.

Please note:
Even if you have sexual intercourse shortly before ovulation, there is a probability of pregnancy because the sperm can survive for up to two days and fertilize the ovulum. However, the egg cell itself only has a lifespan of about one day. Therefore, if you do not want to become pregnant, you should refrain from having sexual intercourse during the fertile days and shortly before and shortly after.

How often does ovulation take place?

During a cycle, there is usually a single ovulation. However, it is possible that no ovulation occurs at all. This is the case, for example, for women who are under a lot of stress or who suffer from certain diseases, such as endometriosis, ovarian cysts or thyroid diseases. Similarly, ovulation can also fail to occur in the case of strong hormonal fluctuations and in the phase before menopause.

In very rare cases, two ovulations per month can also occur. Consequently, in pregnant women who are expecting fraternal twins, two ovulations took place at the time of fertilization.

When does ovulation take place?

When ovulation occurs depends on the length of your cycle and your general state of health, among other things. With a regular cycle of 28 days, ovulation normally takes place between 12 to 16 days before the next menstrual period. The increased estrogen level contributes to an increase in the luteinizing hormone (LH). About one to one and a half days after this increase, ovulation occurs. However, if the length of the cycle differs, the fertile days can also vary.

To find out when ovulation occurs in your case, it is best to use our ovulation calculator. You can also use the NFP (Natural Family Planning) method or an ovulation test to find out when ovulation occurs.

How long does ovulation last?

The actual ovulation lasts only 15 seconds, after which the egg cell is optimally fertilizable for 12 hours. Overall, however, it only survives for a maximum of 24 hours. Either fertilization occurs during this period or the egg cell dies and is ejected together with the uterine lining during the next period. However, since the male sperm is active for up to 48 hours, the days before and after ovulation are the fertile days. During this time pregnancy is therefore possible.

Signs of ovulation

There are some signs and symptoms of ovulation. These are not always easy to detect, however, especially if you have been using the pill or another hormonal contraceptive. The body is then “trained” to suppress the symptoms.

If you wish to become pregnant after you stop taking the pill or using another method of contraception, you should pay attention to the following signs of ovulation:

1. The basal body temperature rises

The basal body temperature is a woman’s body temperature measured immediately after waking up in the morning.

Important information:
If you want to use the temperature method for contraception, you must take the measurement immediately after waking up, but before getting up. Before ovulation, the body temperature is in a significantly lower range than after ovulation. The rise in temperature is therefore a sure sign of ovulation.

2. The luteinising hormone level rises

As mentioned above, about one day before ovulation the LH level rises significantly. There are now so-called ovulation tests that measure the amount of this hormone in your urine, so that you can determine the time of your ovulation quite accurately.

3. The cervical mucus changes

The vagina regularly discharges some secretion. The consistency of this so-called cervical mucus changes over the course of the cycle. At the beginning of the fertile days, the mucus not only increases in amount, but also becomes glassier and more transparent. In addition, the texture changes from sticky and viscous to liquid and stringy. This is important because the mucus is responsible for the sperm passing on into the uterus. This is only possible if it is “more active” than usual at the time of ovulation. At the time of ovulation, the mucus then becomes viscous and cloudy again within a short time or disappears completely.

4. The cervix changes

Another clear sign of ovulation or of the fertile days is the change of the cervix. The cervix and uterine neck become softer and softer towards the time of ovulation and are positioned significantly higher up in the vagina than shortly after ovulation. However, in order to feel these changes and thus determine the beginning of the fertile period, some practice through daily self-examination with a finger is needed. The infertile days can be recognized by the closed, hard cervix.

There are also a few women who feel a slight ache in the uterus during ovulation. This is not a clear indication, however.

Ovulation with an irregular cycle

There are many women today who have an irregular cycle. Perhaps you are also affected by this. A regular cycle is 28 days long on average. But even a period of between 21 and 35 days is still considered “normal”.

A cycle shorter than 21 or longer than 35 days is called an irregular cycle. This also includes cycles with deviations of more than 8 days from cycle to cycle. Influencing factors are, for example, stress and a change of location or climate. However, an irregular cycle can also be due to illness.

The problem: It is more difficult to get pregnant with an irregular cycle. This is mainly due to the fact that it is difficult to determine the ovulation period in an irregular cycle. In the best case, you would first have to track your period for several months to get a feel for when the fertile days tend to occur and how long your cycle lasts. The more precisely you can determine this, the better your chances of becoming pregnant.

Unfortunately, if your cycle is irregular, there is also the possibility that you will not ovulate at all, so you cannot become pregnant. You can either have this checked by a gynaecologist or you can find out for yourself by tracking your periods.

In the course of a woman’s life, it happens from time to time that no ovulation occurs in a month. This can be due to various reasons. However, if you find – or feel – that you have not ovulated for several months, it is best to make an appointment with your gynaecologist as soon as possible. Your gynaecologist will find out why ovulation is not taking place.

How to calculate ovulation

There are generally different methods to calculate ovulation. Below, we present three options:

1. Estimating ovulation

As mentioned, ovulation takes place about 12 to 16 days before the next menstrual period. During this period, you can theoretically become pregnant. With this method, however, the exact date of ovulation can only be guessed. This method also assumes that your cycle always lasts exactly 28 days. If you want to get pregnant, this method is therefore less suitable.

2. Calculating ovulation with the ovulation calculator

With our ovulation calculator you will find out within a few seconds when the next ovulation will occur. However, the prerequisite for an exact measurement is that you know the first day of your last menstrual period and that you know how long your cycle usually lasts.

Please note:
The ovulation calculator only provides approximate values. It cannot provide one hundred percent reliable information. However, it allows the period for conception to be significantly narrowed down, which increases the chances of pregnancy.

3. Finding out the time of ovulation yourself through various measurements

There are several ways to determine the ovulation date. You can find out, for example, with an ovulation test, because it shows you when the LH level rises. 

The temperature method is also a good way of narrowing down the ovulation period. Measure your morning basal body temperature and record the results in a printed table. In order to obtain even more accurate values, you should evaluate the cervical mucus or the state of the cervix as well.

This method, also known as “Natural Family Planning” – or “NFP” for short – is suitable, on the one hand, for women who want to become pregnant. On the other hand, it is an excellent natural contraceptive method. For this, however, it is important that you carefully determine all important values every day and act accordingly. If you do not wish to become pregnant, you must therefore either refrain from sexual intercourse during the fertile days or use a condom and/or diaphragm.

This method also proves to be practical because it can provide information about the causes of existing illnesses or discomfort. It is helpful to analyse your tracking results with your gynecologist.

Tips for women who want to have a baby

There are various factors that can promote pregnancy or unfortunately also prevent it. The younger you are, the better your chances of having a child. From 30 onwards fertility drops slightly; from 35 it drops significantly; and from 45 the probability of becoming pregnant approaches zero. From the age of 35, pregnant women are considered to be at risk simply because of their age. Learn more about the wish to have children and how best to get pregnant. The following factors influence fertility:

1. Age

As mentioned, the younger you are, the better your chances of getting pregnant.

2. Nutrition

Unhealthy diet or eating disorders can reduce the chances of pregnancy. After all, the body must be optimally supplied with all important vitamins, nutrients and minerals in order to regulate the hormonal balance in the best possible way. If you consistently have unhealthy diet, the hormonal balance can get confused.

3. Over- and underweight

Overweight or underweight women also have a problem with their hormonal balance, which reduces their chances of pregnancy. An aggravating factor for underweight women is that the body has a kind of protective mechanism that signals to them “You can’t get pregnant. You are too weak.”

4. Stress

Another common cause of women not getting pregnant is stress. In today’s fast-moving times, a great deal is demanded of us. We can hardly catch our breath. This in turn can mess with our hormones. On the other hand, if you are balanced so that the important messenger substances in the brain are in harmony and the hormone situation is optimal, you have a better chance of getting pregnant.

5. So-called procreation stress

Some women with a strong hope to have children do not become pregnant for years despite all attempts and efforts – this might be an emotional burden. Often both partners are frustrated that no pregnancy occurs, even though both have done everything possible to achieve it. Often the increasing pressure of high expectations then leads to persistent stress and uneasiness. If they let go of the often agonising wish to have a child, they sometimes suddenly become pregnant.

6. Medication, drugs, alcohol, cigarettes

An unhealthy lifestyle involving the use of drugs or smoking and drinking alcohol can be a problem, as can the regular use of certain medications.

7. Problems in men

It does not always have to be the woman who is the reason for not getting pregnant. There are also problems in men that can contribute to the fact that no egg is fertilized. A too low sperm count or poor sperm quality are among them. Therefore, it may make sense to have your partner examined as well.

Why the ovulation calculator is not suitable for contraception

In our ovulation calculator we work with average values. However, your individual cycle data may vary. We therefore only recommend a calculation if you know that your cycle is quite stable over several months and the cycle length always remains identical. The ovulation calculator is by no means suitable as a contraceptive.

Nor should you use it to calculate a possible pregnancy. If you are pregnant, you can calculate the birth date here.

Important questions about ovulation

What do “infertile days” mean?

Infertile days are the days within the cycle on which you cannot become pregnant. This is the period between the menstrual period and the beginning of the fertile days and the period after the end of the fertile days until the beginning of the following menstrual period.

Please note:
Intermenstrual bleeding and spotting must not be counted as regular periods. The first day of menstruation should therefore never be determined by means of spotting.

How long am I fertile after ovulation?

After ovulating, you will be fertile for about a day, because the egg cell cannot survive any longer. However, the sperm of the man can survive up to 48 hours.

When can I take a pregnancy test after ovulation?

When you can do a pregnancy test after ovulating depends on the respective test. There are products that show a reliable result just a few days after ovulation. Others, in turn, can only be used about 10 to 14 days after ovulation, as the pregnancy hormone HCG in the urine rises only at this time. Pregnancy tests taken directly at the doctor’s may be more likely to provide information about an existing pregnancy. 

If you are planning your pregnancy using the natural method, NFP, you can also recognize a pregnancy by the fact that your temperature does not decrease again after ovulation but remains elevated.

What is going to happen in the first weeks of pregnancy and how to recognise a pregnancy can best be found out using our HiPP Pregnancy Weeks Calendar.

How can I calculate the week of pregnancy after ovulation?

To calculate the current week of pregnancy or the date of birth, it is best to use the HiPP Pregnancy Calculator. It determines the week of pregnancy either on the basis of the last menstrual period or the date of fertilization. You can also use the calculated date of birth to find out which week of pregnancy you are currently in.

Information about the author:

Anja Schröder, a mother herself, has been writing as a freelancer for several major family blogs for many years. She mainly focuses on family topics and brings her texts to life with her vivid storytelling.

Expert advice and editing: Birgit Laue, midwife & medical pedagogue, graduate PR specialist, author

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