Pregnancy Due Date Calculator : How Many Weeks Pregnant Am I!

 Estimated due date

Determining the conception date

The human egg is capable of fertilization for only 12 to 24 hours after ovulation is done . The date of the ovulation may be taken as being the date of conception. The ultrasound can determine the date of ovulation. It has the same imprecision as does the ultrasound estimate of the gestational age. Therefore, it is true that a precise conception date cannot usually be determined as with in vitro fertilization.

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On the other hand, a woman is most likely to become pregnant if she has sex on the day of ovulation. The conception may also occur when live sperm still in her reproductive tract on the day of ovulation, and it occur, if she had sex for up to 5 days before ovulation.

Determining the estimated due date

The estimated due date (EDD or EDC) is the date when, spontaneous labor is expected to occur. May be the due date estimated by adding 280 days , which is to the first day of the last menstrual period (LMP).
Most of the pregnancy calculator use this method. The accuracy of the estimated due date , which is derived by this method ,always  depends on accurate recall by the mother to be, if assumes regular 28 day cycles, and that ovulation and conception occurs on day 14 of the cycle.

Use of the LMP to establish the due date may overestimate the duration of the pregnancy, and can be subject to an error of more than 2 weeks.

However, in cases where the date of conception is known precisely, such as with in vitro fertilization, the estimated due date is calculated by adding 266 days to the date of conception.

Another method is Ultrasound, which uses the size of the fetus to determine the gestational age.

The accuracy of the ultrasound which estimate of the gestational age, ( called gestational age calculator) varies according to the gestational age. Ultrasound measure the embryo or fetus in the first trimester, it is the most accurate method to establish or confirm gestational age.

Most of the gynecologist recommends that,  ultrasound-established dates should take preference over menstrual dates when the discrepancy between ultrasound dating and LMP


First day of last period

conception date

Ultrasound scan

IVF transfer date

Can I plan my due date?

Can my due date change?

First day of last period

Most of the pregnancies last around at least 40 weeks or 38 weeks from conception date. That's why,  the best way to estimate your baby due date is to count 40 weeks, or 280 days, from the first day of your last period, or you can say last menstrual period (LMP).

There is another way to do it, you have to  subtract 3 months from the first day of your last period and then add 7 days.


If your last period started on April 11, you have to count back 3 months to January 11 and then add 7 days with it, which means your estimated due date would be January 18.

In this way  your doctor will estimate your due date — and it’s also a pretty solid target. But you should always remember: It’s just as normal to deliver 1 week or 2 before or after.

Conception date

Your baby due date calculator based on the 1st day of your last period works well for those women who have a relatively regular menstrual cycle. 

But, It Is also true that, if your cycle is irregular, the LMP method may not work for you. As a reliable estimated due date (EDD) is important, you and your doctor can use your conception date instead if you remember it. You can  just add 266 days to get your estimated due date.

IVF transfer date

If you are the part of the growing tribe of in vitro fertilization (IVF) moms, you can calculate your due date more precisely using your IVF transfer date.

Ultrasound scan

Even if you can’t find out when you conceived, forget the day of your last menstrual period or aren’t sure when ovulation occurred, there is also other clues, that can helps you and your gynecologist to determine your due date at your first prenatal appointment,


An early ultrasound,

An ultrasound, can more accurately date the pregnancy. Just be aware, however, that not all women get an early ultrasound. Some of the doctors perform them routinely, but others only recommend one if your periods are irregular, if you're 35 or older, if you have a history of miscarriages or pregnancy complications, or if the estimated due date can’t be determined based on your physical exam and LMP

Pregnancy milestones

Like as the first time the baby's heartbeat is heard. It is around week 9 or 10, but it can vary.
when you first feel your unborn movement or you can say fetal movement on average between 18 and 22 weeks, but it can be earlier or later. Both of them  can give clues as to whether your due date is accurate.

Your fundal height,

It can b measure from your pubic bone to the top of your uterus, and it is checked by your doctor at each prenatal visit and helps confirm your due date. 

The size of your uterus,

It will be noted when your initial internal pregnancy exam is performed, can also be a factor in pinpointing the EDD or estimated due date.

Can I plan my estimated due date?

If you are trying to avoid being  pregnant in the middle of the summer or are a teacher who wants to maximize the time off with your little one, also you can try to time when you conceive in order to "plan" your estimated due date. But on the other hand even if you're one of the lucky ones who's able to get pregnant when she really wants to, just remember that, you probably won't be able to map out exactly when you'll give birth to the day or even the week or month.


But you can also try some Ovulation Calculator, which uses the date of your last menstrual period and your typical cycle length to discover the days you're most likely to be fertile and increase your chances of conceiving.

Can my due date change?

Yes obviously your due date can change. While it’s definitely not a reason to worry, your gynecologist may change your due date for a number of reasons as your pregnancy progresses.

It may be that you have irregular periods and your early ultrasound dating was off, or that your first ultrasound was in the second trimester.

Your due date also could change because your fundal height is abnormal, or your levels of alpha-fetoprotein (AFP), a protein made by the baby, are outside the usual range. Talk to your doctor if you have any questions or concerns.

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