Calculate Pregnancy Week

Pregnancy calculator for a quick overview

Week of pregnancy ﹣ Pregnancy Calculator

The pregnancy calculator calculates the week of pregnancy, date of birth and much more about your pregnancy.

Using the date of the beginning of your last menstruation and the length of your cycle, the Pregnancy Calculator also calculates typical developmental steps of your child during pregnancy as well as important check-up dates. You will find the scrollable dates in the results window of the Pregnancy Calculator. The calculator provides all data from fertilization to the date of birth.

Please note that the Pregnancy Calculator is similar to our Pregnancy Week Calculator. We have additionally listed it here as a Pregnancy Calculator to make it easier for you (as parents-to-be) to find our calculators from the Medicine and Health section on the internet.

In addition to the Pregnancy Calculator, you may also be interested in our specialised calculators, such as the Birthdate Calculator.

Calculate the birth date of your baby with our Pregnancy Calculator

Maybe you have been working towards it for a long time, or it is very spontaneous and perhaps unplanned, your period stops and you take a pregnancy test. The result? Positive. You are going to be a mother! One of the first questions that will now arise: When is it time? When will I hold the "new earthling" in my arms?

This is not as easy to calculate as many people think. Expectant mothers usually only become aware of their pregnancy when their period stops. At this point, they are usually already in the fifth or sixth week of pregnancy. Therefore, the positive test in the hands can neither be equated with the actual start of the pregnancy nor does the inclusion of ovulation suggest this.

An exact calculation would only be possible if the ovulation stage at the time of fertilization is known. However, very few women know this. For this reason, a Pregnancy Calculator, such as the one you can find here, is useful. In this way, you can find out when you will be able to cuddle with your “little miracle” for the first time.

How our Pregnancy Calculator works

Our Pregnancy Calculator is based on the day of your last menstruation and the length of your cycle. When calculating the gestational age, the start of menstruation is included, even if you are not actually pregnant for the first two weeks of pregnancy. Therefore, the calculation of the expected date of birth is quite confusing, especially if the length of the cycle deviates upwards or downwards from the average 28 days.

And this is how you calculate your week of pregnancy:

  1. Determine the first day of the last period and the cycle length. A cycle always starts on the first day of the period and ends with the day before the next period starts.
  2. Enter the last day of your period and the cycle length into our calculator.
  3. Now click on "Calculate".

The birth date: What role does the cycle length play?

A cycle extends over a period of time that begins on the first day of the period and ends on the day before the next period. The cycle duration can be used to determine the date of fertilization. Together with the average pregnancy duration of 38 weeks in total from the time of fertilization, the expected date of birth can be calculated.

Ovulation and thus possible fertilization take place 14 days before the next period. Depending on the length of the cycle, the expected date of birth is 40 weeks or even a few days more after the start of the last bleeding.

Here are two examples

  • With an average cycle length of 28 days, ovulation takes place 14 days after the first day of the period. In this case, 40 weeks are added for the due date.
  • If the cycle lasts an average of 32 days, ovulation occurs on Day 18 of the cycle and an additional four days are added for the due date.

Formula for calculating the date of delivery

The rule of thumb for calculating the expected date of delivery is as follows:

Date of birth = 1st day of last period + (cycle duration - 14) + 266 days.

40 Weeks - an exciting time at a glance

Our Pregnancy Calculator has now told you the expected date of delivery. You are now facing an exciting time with many changes. We are sure you would like to know what to expect. The next 40 weeks or so will be a time of many appointments for you, first and foremost, the antenatal examinations. Therefore, you will below an overview of all the examinations that you will have in the next few months according to the recommended maternity guidelines.

Preventive medical check-ups according to recommended maternity guidelines

Plan for preventive medical check-ups according to recommended maternity guidelines
Gestation Weeks (GW)Examination
from GW 5Initial examination by a gynaecologist (blood test, possibly cancer screening).
GW 9 to 12Preventive examination and first ultrasound
GW 11 to 13On request, first trimester screening (if necessary), chorionic villi¬biopsy, DNA blood test (from GW 10)
GW 13 to 16Preventive examination
GW 16 to 17Amniocentesis (if necessary)
GW 17 to 20Preventive check-up with second ultrasound, fine diagnostics (if necessary)
GW 21 to 24Preventive­examination
GW 24 to 27Oral glucose tolerance test (check for possible gestational diabetes), antibody screening test
GW 25 to 28Preventive examination
GW 29 to 32Preventive examination with third ultrasound
from GW 32Blood­testing for hepatitis B, from now on every fortnight screening
GW 33 to 34Preventive examination
GW 35 to 36Preventive examination, B streptococcus smear
GW 37 to 38Preventive check-up and, if necessary, CTG to check the baby's heartbeat and possible contractions
from GW 40Check-ups about every two days and CTG and determination of the amount of amniotic fluid.

Your gynaecologist will inform you about all possible examinations at the beginning of your pregnancy. You will also be advised to have a whooping cough vaccination from around the 30th week of pregnancy. The preventive medical check-ups may also take place in rotation with a midwife.

All the results of the individual examinations are recorded. Regardless of the result of our Pregnancy Calculator, the expected date of birth can change again during the first trimester, as the results of the gynaecologist's examinations are decisive for determining the expected date of delivery.

Preparation is the be-all and end-all

Regardless of the expected date of delivery, prepare yourself from now on for the coming weeks and months.

Your body is now working at full speed and has to master many challenges. Keep yourself fit for this, eat a balanced diet and get enough exercise. You should also think about the birth: where, how and with whom should it take place? Together with your partner, look for a name for your baby and create a nice home for him/her. Your nest-building instinct will certainly be stimulated. Find out early on what is necessary for life with a newborn child.

How safe is the Pregnancy Calculator?

Basically, we would like to point out that our Pregnancy Calculator can only provide an estimate of the expected date of birth. You should not rely on this date. Every pregnancy takes a different course and only about four percent of all children actually see the light of day on the calculated date.


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Source information

As source for the information in the 'Week of pregnancy' category, we have used in particular:

Last update

This page of the 'Week of pregnancy' category was last edited or reviewed by Stefan Banse on February 19, 2023. It corresponds to the current status.

Changes in this category "Week of pregnancy"