How To Calculate Your Current SSW

Do you want to know in which week you are pregnant? With our SSW calculator you can easily find out in which week of pregnancy (SSW) you are currently. You can also find out why it is important to know your current SSW. We give you an overview of all 40 weeks of pregnancy and we have compiled answers to the most important questions about weeks of pregnancy.

Pregnancy is one of the most exciting experiences in a woman’s life. Every expectant mother who has just found out about her pregnancy naturally wants to know in which week she is. With our SSW calculator you can calculate your current SSW with just a few clicks. To keep an eye on the development of your child, it is important to know in which week of pregnancy you are currently. Also your own physical development and possible complaints can be classified much better. In addition, you have the possibility to plan all important appointments such as the check-ups and the birth date in time. We give you an overview of all 40 weeks of pregnancy and answer the most important questions.

SSW Calculator

With our SSW calculator you can easily determine your pregnancy week by entering the first day of your last period:

How The SSW Calculator Works

Your gynecologist calculates your SSW at your first pregnancy check-up based on your last period: The first day of your last period marks the beginning of your pregnancy (SSW 1) – even though fertilization has not yet taken place. This is exactly how our SSW calculator works.

To calculate your SSW as accurately as possible, you should enter your average cycle length. Normally, 28 days are assumed. However, if your cycle is longer, the start of your 1st SSW.

Calculate The SSW From The Day Of Conception

Alternatively, you can also enter the day of fertilization or ovulation in the SSW calculator to calculate your current week of pregnancy.

With this date, the determination of the SSW is even more accurate – however, it is usually difficult to determine this day exactly (unless you have undergone artificial insemination). This is because the day of fertilization does not mean the day you had sex, but the time when the egg was fertilized. This can still be the case up to five days after the intercourse.

If you know when you ovulated, it is a little easier to determine. This is because fertilization cannot take place more than 12-24 hours after ovulation.

Why Is It Important To Calculate The Current Week Of Pregnancy?

It is important to calculate the current gestational week for the following reasons:

  • You can plan your check-up appointments in time.
  • If you know the current SSW, you can also calculate the date of birth.
  • You have the possibility to inform your employer about your pregnancy in time, so that the maternity protection periods can be observed.
  • You will know if your baby is developing normally. The certainty will reassure you.
  • You have an overview of your physical development and know whether any complaints are normal for the respective gestational week.
  • You can record the development of your pregnancy in your maternity record.

Your gynecologist or midwife will calculate your SSW at the beginning of your pregnancy. At every check-up, she will check whether your baby is developing healthily according to your gestational age. Since she knows what stage of development is normal in which gestational week, she can also tell you how big and heavy your baby should be in that particular gestational week. Important data that concerns you, such as your weight development and your blood and urine values, will also be compared with the current gestational week.

At each check-up

All Weeks Of Pregnancy At A Glance

Below you will find an overview of all 40 weeks of pregnancy.

1.SSW: New cycle
At the beginning of every pregnancy there is the start of a new cycle. A cycle usually lasts between 24 and 36 days, but can also be longer or shorter. It begins with the menstrual period and ends before the day of the next menstrual period. The 1st SSW is already counted as one of the 40 weeks of pregnancy.

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2.SSW: Beginning of fertility
The 2nd week of pregnancy is the beginning of fertility in your cycle. Your ovaries are working at full speed and one or two follicles are growing, in which the egg is located.

3. 3rd week: Pregnancy takes its course
In the 3rd week of pregnancy, the pregnancy really begins when a sperm has made it to the egg and fertilized it. For the fertilized egg, it is now time to look for a cozy place in the uterus and to divide diligently so that a baby can be born.

4.SSW: Small as a poppy seed and very lucky
Your baby is just the size of a poppy seed this week, and it can already cause so many feelings of happiness in you when you hold the positive pregnancy test in your hand. This moment, which will change your life quite a bit, can possibly occur as early as the end of the 4th SSW.

5.SSW: The little heart begins to beat
The information about the pregnancy is still very fresh and everything feels new to you. Even though you don’t notice much of the embryo yet, a lot is already happening in your body. By the time you reach the end of the 5th week of pregnancy, the little heart is already starting to beat and can sometimes even be seen on ultrasound.

6.SSW: The baby doubles in size
The baby is now growing in your belly for about four weeks, and even though it is still tiny, it is already doing great things. In the 6th week of gestation, the embryo manages to double its size and is already gaining weight.

7.SSW: The baby’s first movements
Of course, it will still be a few months before you can feel the first gentle nudges from your baby. Before that, however, the embryo is already practicing diligently and begins to do so around the 7th week of gestation. It slowly makes its first movements, which are still uncontrolled at the beginning and primarily serve to build up the muscles.

8.SSW: An important time for the development of the senses
Humans are shaped by their senses. Hearing, tasting, seeing, feeling and also smelling are decisive for personal development. An important foundation for this is laid for your baby as early as the 8th week of gestation. Both the eyes and the inner ear are being further developed.

9.Week 9: The formation of the important organs is completed
With the 9th week of pregnancy you enter the third month of pregnancy and the first trimester is coming to an end. All the important organs have now been laid out in your baby. Thus, it leaves the embryonic phase behind. From a medical point of view, it is now called a fetus until birth.

10.SSW: The little person is already almost perfect
At just 3 cm, your baby is still really small in the belly, but it already looks almost like a perfect human being. In the meantime, the toes and fingers have developed even more, the face is already clearly visible and the head has become more erect.

11.SSW: Focus on the development of the sensory organs
Even though your baby is still relatively small in the 11th week of gestation, he or she is already very well developed. The critical phase of organ development is almost behind you. Instead, the focus is now on the sensory organs. The functions of the nose and mouth continue to develop and the taste buds are also slowly emerging.

12.SSW: Hiccups and tooth buds
The first critical trimester is drawing to a close and the sperm and egg have now become a small human being. The organs have been laid out, fingers and toes can be seen. Now it is time for the finishing touches. In this week of pregnancy, the first tooth buds are formed, from which the small milk teeth will later emerge.

13.SSW: Focus on growth and maturation
In the last weeks of pregnancy, it was particularly important to lay all the foundations for the baby’s development. In addition to the creation and growth of the organs, little things like the finger and toe nails have already formed. Now begins the time when your baby is mainly busy growing.

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14.SSW: The lanugo hair grows
Your baby’s little body is now covered by the soft lanugo hair. It serves to protect the skin and falls out before birth. In some cases, babies still have the thick hair on their skin.

15.SSW: Mommy’s voice arrives in the belly
For the baby in your belly, the 15th week of gestation is a real milestone, because now hearing is developed to the point where it can finally hear mom’s voice. In addition to your voice, it is above all the heartbeat that reaches your baby and has a very calming effect on the little person.

16.SSW: Hormone production really gets going
Your baby’s thyroid gland is really busy from the 16th week of gestation, because now more and more hormones are being produced that are important for development. However, it needs support in this process. For this reason, it is especially important that you consume sufficient iodine in your diet.

17.SSW: Activity for training the muscles
Movement is your baby’s current hobbyhorse. He moves through the womb with great pleasure and begins to control his own movements more and more. Up to now, it was often rather random in which direction the movements went, but now your baby is learning to move its arms or legs in a certain direction.

18.SSW: Plenty of sleep for growth
Some women feel as if the baby is always active in the womb at a similar time. In fact, however, no rhythm has yet developed in the 18th SSW that is noticeable. The baby sleeps a lot in the belly. For about 20 hours, it is busy sleeping peacefully and recharging its batteries to continue growing.

19.SSW: The sense of touch is already working well
For your baby, the sense of touch is a very important feature, even in the womb, and it is already quite well developed in the 19th week of gestation. Your baby’s hands or feet are now coming closer and closer to the uterus, and when this happens, your baby pulls his hands or feet back again. In this way, it is now slowly noticing the boundaries in the abdomen.

20.Week 20: Enjoy with all your senses
The 20th week of gestation is another important milestone for your baby, because now everything revolves around the further development of the senses. The sense of smell and taste, touch, hearing and sight are developing better and better. In the meantime, the eyes even react when bright light falls on the belly, even if they are still closed.

21.SSW: The rhythm of the sleeping and waking phases
The baby sleeps around 20 hours in the belly and this sleep is also urgently necessary, because all the developments are a real high performance for the little body. However, by now you may notice certain waking phases in your belly. In fact, babies start to slowly develop a rhythm in the 21st SSW.

22.SSW: The hiccups can be felt
Your baby has been hiccupping for a few weeks, but so far you haven’t noticed. However, this is slowly changing from the 22nd week. In the meantime, the baby has reached a size where, depending on its position, it will also bump against the abdominal wall when shaken by the hiccups.

23.SSW: The distinction between the sounds
Very exciting in the 23rd SSW is the development of your baby’s inner ear bone. This has not yet hardened. As a result, your baby could perceive the sounds, but could not yet differentiate them properly. This is changing now, because the bone is hardening more and more.

24.SSW: Sweet, sour or salty – taste for the baby
Your baby’s taste buds are already well developed, and in the 24th week of pregnancy he or she will begin to notice more and more differences in taste. Your baby will pick up amniotic fluid and taste whether it is salty, sour or rather sweet.

25.SSW: The sense of balance is on the rise
Balancing one’s own body posture is a very big challenge for infants, which must be learned gradually. The basis for this is the sense of balance and this is now being developed in the 25th week of gestation. Your baby is now increasingly capable of influencing its own posture.

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26.SSW: The grasping reflex continues to be trained
The umbilical cord is your baby’s favorite toy. He has a lot of fun catching it, moving it with his little hands and toes, reaching for it and playing with it. This is not only great entertainment for the little person in your tummy, but also an ideal way to train the grasping reflex.

27.SSW: The brain furrows continue to develop
An important focus of development in the 27th SSW is the brain. Until this week, the surface was still relatively smooth. This is now changing more with each passing day, as the brain furrows continue to form. This also has an effect on your baby, because he will probably have his first dreams now.

28.SSW: The fine-tuning of the brain continues
Already in the 27th week, furrows have slowly formed in the baby’s brain. In the 28th week, the brain will continue to be provided with furrows, and the more these increase, the more your baby’s brain activity will increase. In this way, sensory perceptions become more and more differentiated.

29.SSW: Now it’s time to tackle the baby fat
In the 29th week of gestation, organ development has now almost reached its end point, and in the next few weeks the main thing is for your baby to gain more and more weight and size. With a height of just under 39 cm and a weight of around 1,150 g, there is still a lot to do before birth, because the average baby will then be around 50 cm tall and weigh around 3,200 g.

30.SSW: The baby and pain stimuli
The 30th SSW is an important milestone, as researchers have found. The baby is now able to recognize pain stimuli and feel pain. This finding is not that old. After all, doctors were of the opinion that neither fetuses nor babies are able to feel pain.

31.SSW: An important time for the lungs
The 31st week is a particularly important time for the baby’s breathing. The lungs are now so far advanced in their maturation that they are able to inflate. The production of surfacant also continues to increase and ensures that the lungs cannot stick together.

32.SSW: The search for the right position
So far, the baby has still had quite a lot of room in your belly to make the odd turn. Slowly, however, it is getting tighter and tighter, which is why many babies decide to take up their final birth position as early as the 32nd week. You will probably feel this as well.

33.SSW: The rapid growth of the brain
Although the brain is already well developed in the 33rd week, there is still a lot going on in the next few weeks. For example, the circumference of the head increases by more than 1 cm in the 33rd week of pregnancy and this is due to the fact that the brain volume increases significantly.

34.SSW: The lungs are finally ripe
In premature labor before the 34th week of pregnancy, it is mainly the lungs that cause concern. Therefore, there would still be lung maturity to help them unfold. At 34 weeks gestation, lung maturity is finally complete and the baby would normally be able to breathe on its own if it sees the light of day too early.

35.SSW: The baby and his dreams
Did you previously think that your baby doesn’t even dream yet? Researchers have found out that this does happen. It is assumed that your baby is already dreaming very intensively in the 35th week of gestation. The fact that even unborn babies already have an REM phase is particularly exciting.

36.SSW: The search for the starting position
Perhaps you have been working towards the 36th week in the hope that your baby will still turn. Especially if it has been in a breech position so far, this wish is quite understandable. Doctors and midwives give babies until the 36th week to turn on their own. If this has not happened by now, then attempts are now made to coax the baby.

37.SSW: The brown fatty tissue increases
Your baby has already gained a lot of weight in the last few weeks and has put on more and more fat deposits. By the 37th week of gestation, the fat reserves have already increased significantly. This is also particularly important for your baby.

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38.Week 38: Fine-tuning the lungs
In the 38th week of gestation, your baby is ready to be born and it is quite possible that you will already be able to hold your offspring in your arms during this week. However, it won’t hurt the baby to stay in the womb for a few more days, because now the final touches are being made to the lungs. The lungs begin to produce cortisone.

39.SSW: The storage of fat reserves
The 39th SSW has been reached and it can now start every day. The 10th month of pregnancy is coming to an end and your baby is ready for birth. If this is still a little long in coming, then it will continue to use the time effectively, because it will lay down even more fat reserves.

40.SSW: The baby is ready to start
If you have reached the 40th week of pregnancy, then you are officially in the last week of pregnancy and now have 10 months of pregnancy almost behind you. In those 10 months, a poppy seed has grown into a strong baby that’s ready to take off any day now. Your baby is basically ready to start.

The Most Frequently Asked Questions About The Weeks Of Pregnancy


Jörg Baltzer: Praxis der Gynäkologie und Geburtshilfe: das komplette Praxiswissen in einem Band. Thieme Verlag, 2006.

Christine Mändle, Sonja Opitz-Kreuter: Das Hebammenbuch: Lehrbuch der praktischen Geburtshilfe. Schattauer Verlag 2007.

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