HiPP due date calculator: the easiest way to determine your due date

Are you pregnant and you want to know your baby’s due date? We at HiPP have developed a due date calculator that you can use online and free of charge! Learn how to “calculate your due date”.

How do I determine my due date?

For many parents, determining the due date is one of the most important steps after getting a positive pregnancy test. They want to prepare as well as they can for the birth of their little one and everything that comes after. So knowing when their little one is due to arrive is key. However, knowing your due date is also important for medical reasons. It is an important point of reference regarding fetal development.

The estimated due date as point of reference

The estimated due date is the day with the highest probability of birth. But only about 4% of all babies are actually born on this day. However, most babies arrive between two weeks before and two weeks after that day. This period is therefore just as relevant as the estimated due date.

You can determine the due date yourself using a simple formula. However, it’s even easier if you use our HiPP due date calculator.

Due date & pregnancy week

This is how your due date is calculated: An average pregnancy lasts 40 weeks. Pregnancy begins on the first day of your last period. This is also the way doctors and midwives calculate your due date. 

First day of the last menstruation:

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

Please note:
We want to stress that using the due date calculator does not replace seeing a doctor and/or any healthcare professional.

Determining the due date with your gynaecologist or midwife

Midwives and gynaecologists usually do not use an online tool to calculate the due date, but determine the date either mathematically using Naegele’s Rule or with a pregnancy wheel (a kind of pregnancy calendar). According to Naegele’s Rule, the due date for women with an average cycle length of 28 days is calculated as follows:

first day of your last period

+ 7 days - 3 months + 1 year

Here´s an example:
The first day of your last period: 06.07.2020
Plus 7 days: 13.07.2020
Plus 7 days: 13.07.2020
Plus 1 year: 13.04.2021

If your cycle is longer or shorter, you add or subtract the amount of days your cycle deviates from the 28-day average: first day of your last period + 7 days - 3 months + 1 year +/- the amount of days your cycle deviates from the 28-day average.

Determining the due date after assisted conception

When calculating the due date after assisted conception, you normally don’t use Naegele’s Rule. In these cases, doctors calculate the due date based on the transfer date. This means that the starting point of their calculation is not the first day of your last period but the day of the actual conception. It’s hard to pinpoint that day with conventional conception.

With assisted conception, however, doctors know the exact date of conception of your little one. This means that your due date would be calculated as follows: conception date - 3 months - 7 days + 1 year.

Determining the due date when you’re expecting twins or multiples

Expecting more than one baby means that your little ones have to share the limited space inside your belly. That is why multiples are often born a little earlier.

Use our due date calculator to determine the regular estimated due date. Now you have to subtract some weeks as multiples are often born in the period between week 37 and week 38.

Calculating how far along you are

You want to figure out which week you are currently in? That’s super easy with our HiPP pregnancy calculator. Enter all the required data and get your results within seconds.

Below the estimated due date you will find the week of pregnancy you are currently in.

Note: If you are yet to get pregnant, you can use our HiPP ovulation calculator to determine your most fertile days.

Why you should know your baby’s due date

Apart from being curious about the day you will finally meet your little one, there are several important reasons why you should know your estimated due date: 

1. Reassurance

Pregnancy is quite an exciting time, no matter if you are expecting your first or third child. As parents-to-be, you’ll certainly be looking forward to the birth of your baby. So finding out when you’ll finally be able to meet your new family member provides a sense of ease and reassurance.

2. Preparation

Knowing when your baby is due makes it easier for you to plan everything. For example, you know when to schedule your antenatal class. We recommend you start the class around week 28 and be done with it at least 4 weeks before your baby is due to arrive. You will also know when it’s time to pack your hospital bag.

3. Notifying your employer

Inform your employer as soon as possible about your pregnancy. This will help you and your employer have necessary adjustments and preparations related to your work.

4. Planning your parental leave

Parental leave is a similar concept and is scheduled to start on the day of the estimated due date. This means that parental leave refers to the time after birth in which you are allowed to stay at home and raise your child.  

5. Applying for child benefit

You are also entitled to child benefit from the day your baby is born. This will always be dependent on your arrangement with your insurance company.

6. Registration at the clinic or birth centre

Remember to register in due time at the hospital or birth centre where you want to give birth or with your doctor (or midwife).  

7. Registering the child’s birth

Law requires you to register your baby. The civil registration office will then issue the birth certificate. Do you already know our checklist for necessary for the registration? 

How accurate is the estimated due date?

One thing is certain: The estimated due date is usually not the actual date of delivery. Various factors play a role in the calculation of the due date. For example, if you cannot tell exactly when the first day of your last period was, the result may differ by a few days. Having longer or shorter cycles can also lead to deviations from the due date.

Also, while pregnancy usually lasts 40 weeks – some children take a little longer, while others are born earlier. All of this is perfectly normal. This means that you should not fixate too much on the estimated due day.

If the estimated due date is 13 April 2021, as in our example, your baby may well arrive between 3 April 2021 and 23 April 2021. Deviations of plus/minus ten days are quite usual. Babies born well before the due date, i.e. before week 37, are considered premature babies.

Reasons why some children arrive early or late

As mentioned above, there are several reasons that can affect the length of pregnancy. In the following, we would like to discuss the most common reasons for an earlier or later delivery.

Why are some pregnancies shorter?

  • Miscalculation of the due date
    Even if the due date calculator is quite easy to use, the due date it suggests might still be incorrect. Reasons for that could be that you’ve entered your data incorrectly (e.g. mistyping) or because you do not know the exact date of the first day of your last period. To avoid miscalculations due to typing errors, always double check the data you’ve entered before clicking “calculate now”.
  • Psychological factors
    Emotional stress can have a negative impact not only on your own health, but also on the health of your unborn child. That’s why it’s particularly important to take care of yourself during pregnancy. Due to hormonal fluctuations, many women are more susceptible to emotional stress during pregnancy. Worries about their child, about their financial situation or about their relationship can add to that stress. All of this will have an effect on their body. For example, it has been proven that people who suffer from permanent stress are more susceptible to infections or diseases. It is this high susceptibility to infections that can lead to complications during pregnancy, causing the baby to be born too early.

Important information:
Avoid stress as much as possible during pregnancy. Allow yourself to relax. By the way, even if you don’t feel bothered by the stress you have, it can still have adverse effects if it becomes too much.

  • Placental insufficiency
    Placental insufficiency is one of the most common causes of preterm birth. In the case of insufficiency, the placenta that supplies the unborn child does not function properly or does not function at all. This can be dangerous for the baby, increasing the risk of premature birth. In some pregnancies, this complication can become so severe that early delivery becomes necessary.
  • Bacteria causing premature labour
    Bacterial infection of the birth canal can trigger premature labor. This means that the risk for a premature birth increases.
  • Alcohol, drug and nicotine consumption
    Drinking alcohol, smoking or taking drugs during pregnancy can significantly damage your baby’s development! Affected babies are often born much too early and are usually seriously ill or even disabled. Additionally, these children struggle with agonizing withdrawal symptoms while still in the womb and even more so after birth.
  • Premature birth due to a shortened cervix
    The cervix might dilate sooner in women with a shorter cervix. This also means that their babies are born earlier.

Why are some pregnancies longer?

  • Miscalculation of the due date
    The reason for a baby going over may simply be that something went wrong in the calculation of their due date.
  • Maternal age
    It is a proven fact that the babies of older mothers are born later than those of younger mothers. This means that it is perfectly normal for the baby of an older mother to arrive some days late.
  • The fertilized egg nested late
    It may be that the egg took a little longer than normal to nest in the uterus. This can also push back the due date.

By the way:
Have other children of yours also gone past their due date? Then there is a high probability that this baby will also be born later than estimated.

Getting ready for the birth of your little one

Even though the due date is calculated, a baby may well be born earlier. For many first-time parents this fact is associated with a certain level of unease. Many of them would prefer a more plannable birth.

The exact date of birth, however, is difficult to predict. Actually, only 4 percent of babies are born on the day predicted by doctors, midwives or a due date calculator.

That’s why you should prepare for birth in due time. This way you can be sure to be ready for when your little one finally decides to arrive into this world – even if they do so a bit earlier than expected. We therefore recommend you also have your hospital bag packed and ready. It should contain clothes for you and your baby as well as important documents such as your maternal health record.

What if my baby goes over?

Usually, there’s nothing to worry about if your baby is born a few days late. Once you’ve passed the due date, your gynecologist (or your midwife) will check that your baby is still well every two days.

If there are still no signs of labor after several days, birth can be induced. However, as long as your baby is doing well inside your womb and there is no risk of complications, doctors (and/or midwives) will usually wait for labor to start naturally.

The most important questions about the due date

What method is best for me to calculate the due date?

You have several options to accurately establish the due date. For example, you can use our practical due date calculator. Simply enter the first day of your last period and the average length of your cycle and click on “calculate now”. Your gynecologist can also determine your due date. To do so, they will need the same information you would enter in our calculator. You can determine the date even more accurately if you know when your little one was conceived.

Can I determine the date of conception?

If your baby has already been born and you want to determine when they were conceived, you can of course do a reverse due date calculation. This means that you subtract nine months from the date your little one was born and then you add seven days. Assuming your baby was born on 1 July 2020, deducting nine months would bring us back to 1 October 2019. After adding seven days we would end up with the estimated conception date being 8 October 2019. 

Why are some babies born earlier?

There are several reasons why some babies are born earlier. A pregnancy normally lasts 40 weeks, but some babies simply want to arrive a bit earlier. Common reasons for a shorter pregnancy are maternal psychological stress, miscalculation of the due date, pregnancy complications such as placental insufficiency or a shortened cervix, and bacterial infection of the vagina. Maternal addiction to alcohol, nicotine or drugs can also lead to premature birth.

Why is it important to know your exact due date?

Knowing the exact due date will put your mind at ease. You now know in what time frame your baby is most likely to be born, allowing you to prepare. You can make appointments at the birth clinic (or your hospital) and with the gynecologist (or your midwife). You know when you should have completed your antenatal class and when your hospital bag should be packed. You can also inform your employer accordingly. The due date is also important for determining the start of maternity leave.

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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