desire for a child, Family Planning

Date of childbirth – Calculate the date of childbirth with a simple formula.

Date of childbirth - Calculate the date of childbirth with a simple formula.

For the calculation of the birth date you do not need a pregnancy calculator.

Just use the date calculator and find out the exact date of birth of your baby! Curious how you can calculate it without technical help? We will tell you!

They always say that babies are born after nine months. But is that really true? How do babies know that they are exactly nine months old? Of course, babies can’t know that. That’s why the delivery date you calculate is always an approximation. We’ll explain why that is, how to use our date calculator, and why it’s not that important to calculate the exact date of delivery.

Simple formula for calculation

If you want to know when your baby is due, you can either use a due date calculator online, or you can grab a pen and paper. The pregnancy calculator tells you more than just the expected due date: You can also calculate the conception date and the current week of pregnancy based on ovulation. The plus days are also displayed.

Enter the first day of your last period into the calculator. You should also enter the average cycle length. This is important because not all women have a regular cycle of exactly 28 days. Alternatively, if you know this, you can enter one of the following dates:

  • the date of the last ovulation
  • the date of conception
  • the date of an IUI
  • the date of IVF
  • the date of ICSI

Your gynecologist, doctor or midwife may have already calculated your due date without digital help. How do they do it? Normally, doctors use the so-called Naegele rule. They start from the first day of the last period and calculate the expected delivery date based on an average cycle length of 28 days. The basic formula looks like this:

1st day of your last period plus 7 days minus three months plus 1 year equals delivery date.

An example: The first day of your last period was January 23. The calculation then looks like this:

  • January 23 plus 7 days equals January 30.
  • January 30 minus three months equals October 30. The year shifts.
  • So the delivery date is October 30 of the current year.

Alternative calculation method

If the Naegele formula is too complicated for you, it is also easier. You can also go from the first day of the last period seven days further in the calendar and then add nine months to the date. Then you will also arrive at the expected date of delivery. However, you should know: This method only works reliably if you have a cycle that lasts exactly 28 days. Deviations are normal, most women sometimes have 27, sometimes 30 days. If you know the exact deviation in your cycle, you can still use the Naegele rule. An extension ensures that you can reliably calculate the delivery date.

With this extended formula, you simply include the deviations from a normal cycle in days.

This looks like this:

Day 1 of the last period plus 7 days plus 9 months plus/minus the deviation in days equals the expected date of delivery.

Calculation of the birth date based on the conception date

You know exactly when your child was conceived? If you know the conception date, we have another method for calculating the delivery date and week of pregnancy for you. The conception date is the time when the egg was fertilized by the male sperm. Be careful not to confuse this with the date you had sex! Sperm can survive in your body for up to five days. You should keep this in mind when determining the conception date.

If you want to calculate the date of delivery as accurately as possible, it helps if you know the day of ovulation. After ovulation, the egg can only be fertilized within 12 to 24 hours. Maybe you can feel your ovulation? For many women, ovulation is felt as an unpleasant tugging sensation in the lower abdomen. However, ovulation can also be detected using the temperature method. Have you been trying to get pregnant for a while? Then you may have used an ovulation test and know exactly when you ovulated.

This is your calculation:

Conception date minus 7 days plus 3 months plus 1 year equals expected delivery date.

Alternatively, you can simply add seven days and nine months to the conception date.

How does the calculation for artificial insemination work?

It doesn’t matter whether you have chosen IUI (intrauterine insemination), IVF (in vitro fertilization) or ICSI (intracytoplasmic sperm injection): We calculate the delivery date from this date. This is because we assume that it is the conception date. So you can simply use the date calculator “after conception”.

Important: Even in this case, the delivery date calculated here is only a guide. Because every pregnancy is individual. When your child is ready to come into the world depends on your age and health, your stress level and many other things. Even with twins and multiples, the calculated date is not correct. Because multiples have to share the space in your belly. That’s going to be a tight squeeze! Twins are often delivered around the 37th week of pregnancy (SSW). On average, they are born three weeks earlier than singletons.

Calculated date of birth versus actual date of birth

You have certainly heard many stories in your circle of acquaintances about babies who came into the world several days or even weeks before or after the calculated date of delivery, possibly even with medical assistance. Why do we calculate a birth date, even create digital date calculators and pregnancy calculators, when babies don’t stick to the calculation at all?

Only about four percent of all children are born exactly on the calculated date! The others decide sometime between the completed 37th SSW and the completed 42nd SSW that they have had enough of the tight belly. All children born within this period (37th week to 42nd week) are considered to be term babies.

Different pregnancy calculators, different dates?

That can also happen. There is a very simple reason for this: the different online calculators sometimes take into account the exact number of days in the month, and sometimes they do not. This means that if the tool is programmed to assume standardized month lengths of 30 days, the calculation will not come up with the exact date. This is because some months have 31 days. February has fewer days. Let’s take a closer look:

If you add the days of the nine months April to December, you come out with 275 days. This is the case in every year, always and without exception. If you add the days of the nine months September to May (of the following year), you get 273 days. If you assume a leap year, it is 274 days. If you notice deviations of one or two days when calculating the delivery date, this is not your fault, but the fault of the tool. Everything is fine! After all, you now know that your baby will probably only roughly follow the calculated date anyway.

Calculated date of childbirth gives orientation

We don’t calculate the birth date because we want to book a fixed night in the hospital. Since only about nine percent of babies are even born on the calculated date, this would be a rather uncertain thing. Please do not plan your vacation, concert visits or other appointments after the calculated delivery date! You need the date for another reason: The upcoming birth must be communicated to an official place. Please do this as soon as you have calculated the date of delivery:

  • Enroll in a childbirth preparation class.
  • Find a midwife who will care for you during pregnancy, birth and postpartum.
  • Inform your employer.
  • Determine the maternity protection period: You are not allowed to work until the birth!
  • Plan the parental leave and discuss everything with your employer.
  • Register at the clinic or birth center.

However, you cannot apply for parental and child benefits yet, because the calculation of the date of delivery is not exact. For these applications you need the actual date of birth. All the best for you and your baby!

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