Calculate The Date Of Birth: When Will My Baby Be Born?

Are you pregnant and want to know when your baby will be born? We show you how you can easily calculate the due date. We also explain why it is so important to know the date of birth and what reasons there are for a shortened or prolonged birth. You can find all the important information and answers to important questions here.

If you want to know when your baby will be born, you have several options for calculating the due date. You can easily use our birth date calculator by entering the first day of your last period and the length of your cycle.

You can also ask your gynecologist or midwife to calculate your due date. There are many important reasons to calculate your due date in time. For example, you will be able to prepare yourself much better and more relaxed for the birth of your baby. But also when it comes to parental leave and maternity.

How Do I Calculate The Due Date?

If you want to prepare yourself optimally for the birth of your child, you should also calculate the due date. The calculation is one of the most important steps after a positive pregnancy test.

Birth Date Calculator

This is how the birth date calculator calculates: An average pregnancy lasts 40 weeks. The pregnancy begins on the first day of the last menstrual period. Doctors and midwives also calculate according to this method.

This Is How The Birth Calculator Works

You enter the first day of your last period into the calculator. Then click on “Calculate now” to display the result. Of course, the birth date calculator does not replace a visit to the doctor.

Calculated Date As A Reference Point

The calculated date (ET) is the day with the highest probability of birth. However, only about 4% of all babies are actually born on this day. Most see the light of day two weeks before or after. This period therefore also counts as the calculated date.

Calculate Birth Date At The Gynecologist

Gynecologists do not normally use a calculator to calculate the due date. They determine the values either according to the so-called “Naegel’s rule” or with a gravidarium. This is a type of pregnancy calculator.

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You can calculate the due date according to Naegel’s rule with a normal cycle length of 28 days as follows:

First day of the last menstrual period + 7 days – 3 months + 1 year

First day of last period: 07/06/2020+
7 days: 07/13/2020-
3 months: 04/13/2021For

a longer cycle length, add the deviation in days to 28, for a shorter one subtract it: First day of last menstrual period + 7 days – 3 months + 1 year +/-deviation in days to 28.

Calculate The Date Of Birth For Twins Or Multiples

For twins

Calculating The Due Date After Artificial Insemination

If you want to calculate the due date of your baby after artificial insemination

Conception date – 3 months – 7 days + 1 year.

This Is Why You Should Know Your Baby’s Due Date

Of course you are curious about when your baby will be born. But there are good reasons why you should know the date of birth. We have compiled the most important ones for you.

1. Reassurance

Pregnancy is a very exciting time, not only for your first child, but also in general. That’s why you want to spend this time as calm and relaxed as possible. If you know the approximate date of birth in advance, you can be much more relaxed about it.

2. Preparation

If you can calculate the date of birth, you can also prepare yourself well for the birth. For example, you can better plan the date for the birth preparation course. This should be completed four weeks before the birth, so you should start it in the 28th week of pregnancy. You can also pack your hospital bag in

3. Employer And Maternity Protection

The Maternity Protection Act states that expectant mothers should inform their employer of the date of birth as soon as they know it. However, there is no legal obligation to do this immediately. But the employer and also the health insurance company need the date of birth to calculate the time for maternity protection.

In Germany, maternity protection begins six weeks before the calculated date of birth and ends eight weeks after the birth. In the case of premature and multiple births, maternity protection is extended to 12 weeks before and after the birth (also applies to premature and cesarean births).

In some professions you are not allowed to work during pregnancy, because it is too dangerous for the child. Your employer must then give you time off and find a replacement for you. Therefore, it is important that he knows the date of birth as soon as possible.

4. Determination of Parental

The same applies to parental leave, which is also calculated from the date of birth. During parental leave, you can stay at home and concentrate fully on your new everyday life with your baby. During this time, you will receive the corresponding parental allowance from the state. This is not to be confused with child benefit. Parental leave usually lasts 12 to 14 months. It can be claimed by the mother as well as the father or by both parents.

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5. Claiming Child Benefit

Another good reason to calculate the date of birth: Entitlement to child benefits also starts on the day the baby is born.

6. Applying For Social Benefits And Assistance

In Germany, you have the possibility to apply for some social benefits for you and your newborn. This includes, for example, the initial baby equipment

7. Registration At The Clinic Or Birth Center

You should register at a birth clinic in good time before the birth. If you prefer a birth center, you must inform your midwife in good time. In order for the obstetricians to be able to prepare properly for the time of birth, you should calculate the date of birth and pass it on.

8. Search For A Midwife

A midwife is at your side before the birth as well as during and after the birth and supports you. Normally, your health insurance will cover the costs. However, there is also a time frame before and after the birth, so the date of birth plays an important role.

9. Registration Of The Child At The Registry Office

Section 18 of the Civil Status Act (PStG) stipulates that you must register your baby at the registry office within seven days of the birth. There you will also receive the birth certificate

What Is The Exact Date Of Birth?

As you have probably already guessed, the calculated date of birth is not the actual date of birth. Various factors play a role in calculating the date of birth. For example, if you don’t remember exactly when the first day of your last period was, the due date may differ. Often the cycle is longer or shorter. This can also influence the date of birth.

In addition, although a pregnancy usually lasts 40 weeks, some children take a little longer, while others are born earlier. This is also normal. You can orient yourself to the calculated day, but you should not get too attached to it.

If the stated date of birth is, as in our example, on 13.04.2021, you should keep an eye on 03.04.2021 to 23.04.2021 as a normal period. Deviations of plus/minus ten days do occur. However, if the baby is born much earlier, before the completion of the 37th week of gestation, this is a premature birth.

Reasons For A Shorter Or Longer Pregnancy

There are various reasons that can affect the length of pregnancy. In the following, we will show you the most common reasons for a shorter or longer pregnancy.

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Shortened Pregnancy

  • Date Was Calculated Incorrectly
    Even if it does not seem to be difficult to calculate the date of birth, it can happen that the date is wrong. This happens when you enter wrong dates. It can happen that you mistype or do not remember the exact date of your last period. To avoid incorrect calculations due to typing errors, you should check the data beforehand and perform the calculation several times.
  • Psychological Factors
    If you are not feeling well psychologically, this can affect not only your health, but also the health of your unborn child. Therefore, it is especially important to take care of yourself during pregnancy. During pregnancy there are often hormonal fluctuations that can affect your state of mind and cause mental imbalance.

Worries about the child, about the financial situation or about the relationship can increase other stress. This in turn has an effect on the physical state. For example, it has been proven that people who suffer from permanent stress are more susceptible to infections or illnesses. It is this high susceptibility to infections that can lead to complications during pregnancy, so that the baby is born too early

Placental Insufficiency
Placental insufficiency is one of the most common causes of premature birth. The placenta, through which the unborn child is supplied, functions only slightly or not at all in the case of insufficiency. This can be dangerous for the baby, increasing the risk of premature birth. Some children then have to be delivered immediately.

  • Premature Labor Due To Bacteria
    If a bacterial infection of the birth canal occurs, this can trigger premature labor. The baby is then more likely to be born prematurely.
  • Alcohol, Drug And Nicotine Use
    If you drink alcohol, smoke or take other drugs during pregnancy, you can cause great harm to your baby. Affected babies are often born much too early and are usually seriously ill or even disabled. In addition, these children already struggle in the womb and increasingly after birth with terrible withdrawal symptoms.
  • Premature Birth Due To Shortened Cervix
    If the cervix is shortened, the cervix may open earlier. The baby is therefore born earlier.

Prolonged Pregnancy

  • Date was calculated incorrectly
    Even if the baby is born later than expected, it is usually simply because the due date was calculated incorrectly.
  • Age of the mother
    It is a proven fact that children of older mothers are born later than children of younger mothers. Therefore, a baby born to an older mother may be born a few days later.
  • Egg has nested late
    It may be that the egg took a little longer than normal to implant in the uterus. This can also push back the due date and does not pose a risk to the baby.
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Rest And Relaxation Until Birth

The most common reason a baby is born before or after the calculated due date is actually miscalculation. It is also not unusual for a baby to take a little longer. So you do not have to worry unnecessarily. If you suddenly feel any discomfort, do not hesitate to see a doctor. Better safe than sorry. It is important that you keep regular doctor’s appointments and get enough rest and relaxation.

The Most Important Questions About The Due Date


Markus Vieten: Handbook for midwives: by midwives for midwives. Thieme Verlag, 2000

Brigitte Holzgreve: 300 questions about pregnancy. Gräfe und Unzer, 2012.

Ulrich Drews: Pocket atlas of embryology. Thieme Verlag, 2006

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