Pregnancy Due Date Calculator – How Many Weeks I Am?

Learn how to use our Pregnancy Due Date Calculator and gain knowledge about ovulation, pregnancy tests, and the usefulness of various calculators and calendars. Please be mindful that most babies aren’t born on their ‘due dates’. Babies come in their own time.



Enter the date of the first day of your last menstrual period (LMP):



Probable date of conception:


Foetal Age Today:


Best date range for NT scan:


(12 weeks 3 days to 13 weeks 3 days)

Morphology Scan Date:


(19 weeks)

First Heart Tones by Doppler:


(11 to 12 weeks)

Best time to evaluate cervical length in patient with risk factors:


Best time for routine anatomy ultrasound:


(18 to 20 weeks)

Estimated Due Date:





A lot of women wonder when they conceived. The conception date can only be estimated based on a reliable pregnancy due date. This pregnancy due date can be obtained using 1 of 2 ways. First of all, a doctor or OB provider may ask the woman if she’s had regular periods up to the point that she got pregnant. And if she was having regular periods. It’s pretty easy to calculate a reliable pregnancy due date calculator based on the woman’s last menstrual period date.

What If Your Periods Were All Irregular?

If a woman’s periods were all irregular the doctor may determine that an ultrasound is warranted early in the pregnancy. Fetuses grow at a very consistent rate during early pregnancy. Therefore, if an ultrasound is done and the baby is measured to be 7 weeks and 2 days, for example. Then they are reliably 7 weeks and 2 days at that point. The due date can be established based on that baby’s measurement. And again, this is a very reliable way to calculate a woman’s due date.


so based on either of these reliable methods, an approximate conception date can be calculated. the reason why I say approximately is that conception happens when the egg and sperm meet up, and this is only possible when a woman ovulates. Typically speaking, ovulation happens about mid-cycle or about 12 to 16 days before a woman’s next period is going to begin, so it really depends on how long a woman’s cycles are and when exactly she ovulated, and it’s not always possible to know that.


Exact Pregnancy Due Date Calculation

This article is about how to calculate your expected delivery date when pregnant. It is important to know your delivery date or due date of the baby’s birth during pregnancy. The pregnancy due date calculation can be done in 3 simple steps which are:


  • The Expected delivery date (EDD) calculation is based on the Last menstrual period date (LMP) and it is applicable only for women having regular menstrual cycles.
  • Pregnancy can last from 38 – 42 weeks.
  • If you do not know your last period date, the pregnancy delivery date can still be calculated based on an early ultrasound scan.


But it is very difficult to determine when ovulation takes place for everybody. Ovulation can vary even for a regular cycle. What we know for certain is that it’s usually 9 months and 1 week. In a regular cycle, your conception would have happened 2 weeks later. This is even how the ultrasound determines the expected date of delivery. So there is uniformity between the ultrasound date and the clinical date because we know that in the first 2 weeks, you are not pregnant, but it is still taken into account keeping the pregnancy duration as 40 weeks when the last periods start. So we calculate the expected date of delivery from the first day of your last period.

How Many Weeks Am I? And What Is A Pregnancy Due Date Calculator?

Before your bundle of joy arrives, you’ll want to know your pregnancy due date as accurately as possible to prepare for that time. If you find yourself asking “How many weeks am I?” you can easily estimate your due date. Healthy pregnancies last about 40 weeks or 280 days from the first day of your last period. An effective due date calculator adds 280 days onto the first day of your last period.

The conception calculator is just an approximation

Keep in mind that a conception calculator is just an approximation, as only 5% of women give birth when they think they will. It’s all up to your little one to determine when he or she wishes to arrive. Past childbirth history or even your mother’s childbirth history could provide important clues as to when your expected due date may be. Once you’ve calculated your pregnancy due date, begin shopping for all the baby gear you want and prepare your home and family.

Here is a chart of pregnancy estimated due dates:

pregnancy due date calculator

Use Of Ultrasound To Calculate The Pregnancy Due Date

A fetus will grow at a pretty consistent rate during the first trimester, and so when they did the ultrasound at 6 weeks and figured that your baby was 6 weeks along, that’s the best and most accurate thing that we can go by. In fact, if a baby starts to be either larger or smaller than it should be in the 2nd or 3rd trimester, a lot of times we ask, “Did she have an early ultrasound?” because that’s the best way to figure out if our due dates are accurate. So because your due date was based on an early ultrasound, you can say that it’s really accurate – as accurate as we can get.

Extra weeks Measure By Pregnancy Due Date Calculator

So you also had some questions about the extra weeks added on at the beginning of a pregnancy when you weren’t actually pregnant. And this does get pretty confusing for a lot of people. Conception happens at the time you ovulate when the sperm and egg meet up. And ovulation usually happens about mid-cycle, or about 2 weeks after your period started.


You won’t find out you’re pregnant until the time of your missed period, or 2 weeks after conception, but at that point, you’re considered to be 4 weeks along. It’s been 4 weeks since your last period, but the baby has actually only been growing for 2 weeks. So that’s where it gets confusing.  the first week of the 40-week gestational period is actually the first week when you were having your period in the cycle that you actually got pregnant in. That’s all a little bit confusing but just go with it since your doctor gave you an accurate due date based on an early ultrasound. Then you can pretty much say, “Yep, I’m due on this date”.

How Does A Doctor Determine Babys’ Due Date?

First of all, it’s important to seek early prenatal care before 13 weeks gestation. And at that point, the doctor will ask you if you’ve had regular cycles in the past and when your last period happened. If you know what date that was and you’ve been regular in the past, then the doctor can pretty reliably calculate a due date off of that because a woman is fertile for 6 days out of each cycle – 5 days leading up to ovulation and on the day of ovulation.


We know that because you had a period, you weren’t pregnant at that point in time, so you got pregnant during that next cycle when you ovulated and the egg and sperm met up. If you had irregular cycles in the past or you’re not sure when your last period was, then the doctor may send you for an early ultrasound. And this is where they measure the size of the growing fetus, look at growing structures, and determine your gestational age from that because a fetus will grow at a very consistent rate during the 1st trimester. So if your baby is measuring 8 weeks, you’re reliably 8 weeks along.

The Amount Of Time The Baby Has Been Growing

Now there’s also some confusion surrounding the amount of time the baby has been growing versus your gestational age. The entire gestational period is 40 weeks. However, a baby only grows for 38 out of those weeks, because the first 2 weeks of the gestational period are from the time of your first period till the time of ovulation and conception. So the baby is not actually growing for those first 2 weeks, so that confuses some people. They get caught up in the fact that the doctor told them they were 8 weeks, but the baby has only been growing for 6 – you’re just 8 weeks gestation. We standardize it across the board.


Now another commonly asked question is, “Will my due date change if my baby is measuring abnormally small or large later on in pregnancy?”. Now I told you that in the 1st trimester, a fetus will grow at a very consistent rate, but thereafter, it can differ. And there are underlying causes that can make a baby be abnormally small or abnormally large, and those are the things that a doctor needs to consider – not changing the due date. So let’s say, for example, that you have an ultrasound at 8 weeks, and the doctor knows reliably how far along you are, and what your due date is.

Reasons That Can Change Your pregnancy Due Date calculation

Later on in the pregnancy, if you have an ultrasound at 28 weeks for whatever reason and the baby is measuring 32 weeks, they won’t just change your due date. And there are a couple of reasons for that. Number 1, a doctor needs to consider underlying causes and decide if further investigation or treatment is necessary for that. And the 2nd is that if the doctor actually changed your due date and put you a month ahead, that’s not going to change how much time the baby has spent growing in the womb, and their organs won’t be fully mature when the baby is full-term. If you have more specific questions about your situation, don’t hesitate to talk with your OB provider, and they’ll be able to give you the best advice and information based on their knowledge of your situation.

What Actually Is A Pregnancy Due Date?

pregnancy due date calculator

We actually see a lot of confusion over what is the due date. So for those who may not know, it sounds like the day your baby will arrive. And is that what it is not really? The scientific term we use is EDC which means the estimated date of confinement sounds pretty old-fashioned. And it is because back before we had a lot of modern technology we dated.  Pregnancy from something we could identify on a calendar, due date was about the average length of pregnancy. After all it’s just an estimation and every one is different. So the EDC is calculated in two ways:

When You Get A Positive Pregnancy Test

One is from the actual first day of the last menstrual period. So if you really think about it you realize you’re not pregnant for the first two weeks of pregnancy. You don’t get a positive pregnancy test until at least week four at the earliest of pregnancy. And then the EDC or the due date is week 40. You get a positive pregnancy test at about week four.  40 minus 4 equals 36. So that’s where we kind of get the nine months of pregnancy colloquial term. How long does pregnancy last? Pregnancy we usually talk about in weeks. Most women, ovulate in the second week of their cycle and so this is how we contribute to the estimation. But not all women ovulate at the same time.


Can a pregnancy due date through the calculator be changed?

Now due dates in general are calculated based on your last period. If you’re having normal cycles because you ovulate sometime usually mid-cycle. So if you have a period and then don’t have another one you know you got pregnant. Sometimes during that month. Ovulation isn’t a perfect science most women ovulate 12-16 days before their next period is going to start. But some ovulate a little bit earlier than that and some a bit later. And that can throw off their due date a little bit. And the doctor might decide to change it if an ultrasound is done.

When Is A Good Time To Deliver A Baby?

It’s one question that every woman thinks about when she is pregnant. When am I going to have my baby? Now, most women deliver sometime between 39 and 40 weeks. Sometimes you go over your due date. Very few women actually deliver on their actual due date.

It’s going to be easier to determine when you might deliver once you get a little bit further along. For example, if you started contracting and dilating a little bit when you are 34-35 weeks, the doctor might predict that you will deliver sooner rather than later.


What To Do If Baby’s Due Date Has Passed

Generally, nowadays all are educated and obstetricians know the dates. It is not good to cross the dates as circulation is reduced. And the water also gets reduced.

Is It Good To Deliver The Baby After 40 Weeks

It is not good to deliver the baby after 40 weeks. What we see is if a baby has crossed the date the baby can die. And this is not good for the mother because she has harbored the baby for 9 months. Because you have crossed the date you have to try for normal delivery also. Most of the time when an Overdue Pregnancy happens. We take an ultrasound of the child and check for the brain of the child. And other organs of the child and then we try to decide what is most appropriate. And how to handle it.

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