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Pregnancy Due Date Calculator | Pregnancy Calculator

When did your last period start?

Calculate your due date

Your baby is likely to be born on or around*

Pregnancy progress…

Stages of your pregnancy:

Your last cyle started on

Your Fetal age

First Heart Tones by Ultrasound (6 weeks)

Best date range for NT scan (11 weeks to 13 weeks 6 days)

Best time to evaluate cervical length in patient with risk factors

TIFFA Scan (scan to detect anomalies) (18 to 20 weeks)

Estimated fertilization date

1st Trimester

2nd Trimester

3rd Trimester

Your due date is

*Only your physician can accurately determine your due date or the date of your conception based on his/her knowledge of your complete medical condition.

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How to calculate your expected date of delivery?

You can calculate your expected delivery date by following the steps below.

Using the date of your last menstrual period :

Usually, pregnancies last for 40weeks or 280days from LMP(last menstrual period), and Just 4% of babies are born on the expected delivery date. One may go into labor anytime after 37 weeks of pregnancy.

If you have a regular 28day menstrual cycle, you can use the following methods :

Naegele’s rule to calculate your expected date of delivery :

Add seven days to the first day of your last menstrual cycle, and then subtract three months.

— Naegele’s rule

for example, if your LMP(last menstrual period) is on October 1st, 2022 then you need to add 7 days to Oct 1st that is Oct 8th and then subtract 3 months i.e, July 8th, 2023.

Using conception date: If you know the ovulation day by tracking ovulation symptoms or ovulation test strips, you can add 266days to get the expected delivery date.

Due date calculation using ultrasound: when your periods are irregular, we need to rely on an ultrasound to determine the gestational age and due date. In the ultrasound, we measure the crown-rump length of the fetus and determine the gestational age.

During the first trimester, the results will be accurate. We call the early scan the dating scan and the most reliable for calculating the expected delivery date.

The dating scan calculated during the second trimester will not be accurate with about two weeks disparity. During the third trimester, there will be almost three weeks disparity 3rd-trimester scan is not used for dating the pregnancy.

How do you calculate your due date if you are unaware of your last menstrual date?

An early ultrasound can determine the fetus’s gestational age; based on that, we can calculate the due date.

How to calculate your due date if your menstrual cycles are irregular?

For some women, menstrual cycles are not regular and have longer cycles like a 35days cycle. Some calculations must be done to estimate the expected delivery date in these cases. Always remember that the second half of a woman’s menstrual cycle lasts 14 days, from ovulation to the next menstrual cycle.

For example: If you have a 35days cycle, you must have ovulated on day 21. Once you get to know when you ovulated, you can use adjusted LMP to find the due date using the calculator

Pregnancy Due Date Calculator: Calculate Estimated Delivery Date

Pregnancy Due Date Calculator

One of the first things a doctor plans after telling a woman she is pregnant is to assess the due date. A normal pregnancy lasts for around 280 days or 40 weeks. Parents spend these 9 months planning for everything that is to be done to welcome the child on the due date. Here, a Pregnancy Due Date Calculator can prove helpful. Read ahead for an overview of this tool.

What is the Estimated Due Date?

The Due Date or Estimated Date of Delivery (EDD) is the provisional date on which a pregnant woman is expected to spontaneously progress into labour and give birth. (The word spontaneously is used here to denote that the progression happened naturally on its own and without any medical intervention.

The calculation for your EDD starts with knowing your LMP (Last Menstrual Period). The LMP is the date of the first day of the last period cycle you had prior to conceiving. The most commonly used methods of EDD calculation are dependent on knowing your LMP date. This method is only used for women who have their periods in a regular monthly pattern. It cannot be reliably used in those whose periods are irregular.

How does a Pregnancy Due Date Calculator work?

The Pregnancy Due Date Calculator is for women with period cycles that last for 28 days, which is the average duration of a cycle. It takes into consideration the starting date of your last menstrual period and the average length of your menstrual cycles. Such a calculator can be found online on reliable healthcare websites such as NHS (UK). You simply have to input the data points mentioned above and it will tell you the EDD. 

It works under the assumption that in a 28 day regular menstrual cycle, ovulation occurs on the 14th day from the start of the period. Ovulation is the process where the egg is released from the ovary into the uterus where it can be fertilised by a sperm cell to form an embryo; colloquially known as conception.

It is important to note that this date is an estimate. Most deliveries happen within 2 weeks on either side of the Estimated Delivery Date, with all that duration within term. In fact, only about 4% of deliveries take place exactly on the EDD!

The estimation of EDD by this formula should always be supplemented and confirmed with the help of an Ultrasound Scan. This is also the method of choice for determining the EDD in those mothers who do not have regular period cycles, or those who cannot reliably recollect their LMP accurately. 

Once you confirm your pregnancy by a urine pregnancy test either at home or at a hospital, you must consult your doctor for an ultrasound scan as soon as possible. This scan, also sometimes called a Dating scan, is done in the first trimester (within 14 weeks) and is the most accurate method to determine how long you have been pregnant as well as the most reliable EDD.  

If the EDD determined by Ultrasound done before 14 weeks of pregnancy varies from the EDD that is calculated from your LMP by more than 7 days, then the EDD should be changed to match the one determined by the scan. 

If you have conceived with the help of techniques like IVF, etc., (Assisted Reproductive Techniques), the age of the embryo and the date of the embryo transfer (the process by which it is implanted in the womb) is taken into account for calculating the EDD and the duration of the pregnancy. 

The importance of knowing the EDD

Determining an accurate EDD during your first pregnancy consultation is extremely important. It is vital information for you to know so that you can plan and be prepared. In clinical practice, knowing your LMP, EDD, and gestational age (how far along your pregnancy is) is critical for planning the following. 

  • visits to the hospital

  • dates of your blood tests and scans

  • dates for initiation of medications, supplements, and vaccination

  • planning the appropriate type of delivery and care for you

Knowing your gestational age and EDD helps your doctor plan your pregnancy in such a manner as to have the ability to diagnose any problems with you or the foetus at the earliest possible juncture.  

Accurate estimation of your EDD and gestational age has a big impact on the course of your pregnancy. If you suspect you are pregnant, make sure to visit your doctor as soon as possible so that you may have a scan done without delay.

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.

Pregnancy and childbirth calculator | University Hospital

The expected time of the birth of a child is a very important date for all parents. It is equally important to know and take into account the periods of pregnancy. For example, there are many important examinations that need to be done in different trimesters.

Use the pregnancy calculator or due date calculator to find out when you got pregnant, the exact number of days you were pregnant, and your due date. The birth calculator also calculates when the second and third trimesters begin during pregnancy. It will also show who the baby will be born according to the horoscope.

Contents of the article

How the date of pregnancy and birth is calculated

Pregnancy is measured in weeks. Since fertilization usually occurs two weeks after the start of the cycle, i.e. around the middle of the menstrual cycle, pregnancy in fact should be counted from the day of conception. But in obstetrics, if the date of conception is unknown, it is customary to count from the first day of menstruation, so a total of 40 weeks is taken into account, that is, 280 days. If we convert the days into months, we get nine and a half months. These extra 2 weeks are just the time before conception.

If the date of conception is known, the estimated time of delivery is 38 weeks, 266 days.

How to use the pregnancy and delivery calculator

The pregnancy calculator is based on the method obstetricians use to calculate the expected time of delivery.

To use the pregnancy calculator, you need to remember the first day of your last menstrual period. Select the desired date in the calendar field, and the calculator will immediately calculate the necessary data online without registration and for free. With the help of the online pregnancy calculator, you will find out the approximate day when the baby will be born. The calculator will also tell you what to pay attention to and what is happening with the fetus and your body this week.

Please note that only 5% of women give birth on the calculated day: births can take place earlier or later, with a spread of up to 2 weeks. Therefore, the expected date is only an indicative and not a final result.

Answers to questions about the timing of pregnancy and childbirth

How to correctly calculate the day of birth?

Most pregnancies last about 40 weeks (or 38 weeks from conception), so a convenient way to determine due date is to count 40 weeks or 280 days from the first day of your last period.

Another way to do this is to subtract three months from the first day of the last critical days and add seven days. So if your last period started on April 11th, you need to count three months to January 11th, and then add seven days. Get it on January 18th. This is how an obstetrician-gynecologist makes an initial assessment of the timing. But remember: giving birth a week or two before or after your due date is just as normal.

How to correctly calculate the date of delivery with an irregular menstrual cycle?

Calculating the due date based on the first day of the last cycle works well for women with relatively regular menstrual cycles. But if your periods are irregular, this method may not work. Therefore, the estimated date of birth is best calculated based on the date of conception. If you remember it, just add 266 days to get an estimate.

Irregular periods

How to determine the exact date of pregnancy: Ultrasound and other clues

If you cannot accurately determine when you conceived, when you ovulated and when your last period was, there are other methods to determine the date of delivery.


  • Early ultrasound. The gestational age is calculated by the size of the fetal egg.
  • Baby’s first heartbeat. Heard at 9-10 weeks.
  • First fetal movement. It is felt between 18 and 22 weeks.

The last two parameters may vary slightly over time.

Parameters indicating the gestational age on examination:

  • The height of the fundus of the uterus, measured from the pubic bone to the top of the uterus.
  • The size of the uterus, determined at the first examination.
Is it possible to plan the date of delivery?

Whether you’re trying to avoid pregnancy because of the mid-summer heat, or you’re afraid of a cold winter, you can plan your birth by planning your conception. To do this, use our ovulation calculator, which allows you to calculate the most favorable days for pregnancy.

Can the due date change?

Yes. Ultrasound can show a different gestational age and a different date of birth. Although this is definitely not a cause for concern. Most likely the reason for this will be irregular periods or a forgotten date of the last menstruation.

It can also be caused by abnormal levels of alpha-fetoprotein (AFP), a protein produced during pregnancy. AFP deviation from the norm indicates multiple pregnancy, miscarriage and fetal malformations.



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Causes and symptoms of late ovulation: is it common?


February 15, 2022



19 December 2019

Reviewed by an expert

How Flo Verifies Facts

All information published on Flo Health follows strict editorial standards for medical accuracy, validity, and timeliness. For more information on how we ensure the reliability of published information, please see our Fact Checking Principles.

If you are trying to conceive or just want to know more about your menstrual cycle, you may find it helpful to read about factors that can cause delayed ovulation.

During ovulation, one of the ovaries releases an egg. It enters the fallopian tube, where it can be fertilized by sperm. If fertilization has occurred, the resulting zygote attaches itself to the lining of the uterus.

If fertilization does not occur, the egg is shed from the body along with the lining of the uterus during menstruation.

Women with a 28-day menstrual cycle will ovulate around day 14. Therefore, with a regular cycle, ovulation occurs about 14 days before the next period.

This makes it much easier for women with regular cycles to keep track of their periods and ovulation.

If you want to get pregnant, you are more likely to conceive if you have sex on the day of ovulation or within 5 days before it.

Is it common to ovulate late? Many women have irregular cycles. According to the study, only 10% of women ovulated on the 14th day. So 28 days is just an average. The duration of your cycle can normally be from 21 to 35 days. This doesn’t mean you’re less fertile, but it can make it harder to predict when you’ll ovulate. In addition, with an irregular cycle, it is more difficult to determine when sex is most likely to lead to conception.

If ovulation occurs after the 21st day of the cycle, it can be considered late.

Late ovulation has many causes. Here are the most common ones.


Some medicines may affect ovulation and fertility. These include:

  • antidepressants;
  • chemotherapy preparations for oncology;
  • thyroid medicines;
  • steroids.

See Patient Information or talk to your doctor if you think a medication you are taking may be affecting your ovulation or fertility.


One of the natural results of breastfeeding is a change in the menstrual cycle. During the entire period of breastfeeding, periods may be absent or irregular. Accordingly, ovulation may not occur.

Polycystic Ovary Syndrome

Polycystic Ovary Syndrome (PCOS) is a common condition that affects the functioning of the ovaries.

Main signs of PCOS:

  • irregular menstruation;
  • high levels of male sex hormones;
  • enlarged ovaries with many follicles.

In women with PCOS, follicle maturation and egg release often do not occur, i.e. ovulation does not occur.

PCOS may be characterized by the following symptoms:

  • irregular or absent menses;
  • have difficulty conceiving;
  • there is increased hair growth on the face and body;
  • observed hair loss, increased oily skin, increased body weight.

Talk to your doctor if you suspect you have PCOS.

Thyroid dysfunction

The thyroid gland is located in the front of the neck. It produces hormones that control heart rate, body temperature and other important indicators of the body. An overactive or underactive thyroid can cause problems with ovulation.

Symptoms of hyperthyroidism include:

  • irritability;
  • mood swings;
  • fatigue or weakness;
  • irregular or unusually fast heart rate.

Symptoms of hypothyroidism:

  • fatigue;
  • weight gain;
  • depression;
  • muscle pain.

See your doctor for advice on diagnosing and treating thyroid problems.


It is natural to experience stress during the day or week. Personal or work issues and a host of other factors can cause you anxiety.

But when life is too stressful or too long, it can seriously affect your body. If your periods have become irregular or you’re having trouble getting pregnant (despite having regular sex), stress may be the cause.

If you think stress is affecting your life and overall well-being, talk to your doctor. He will recommend the appropriate treatment.

Although many women do not ovulate on the 14th day, it is usually considered late if it occurs after the 21st day of the cycle. The best way to track this is to watch for signs of ovulation using any of the following methods.

  1. Measurement of basal body temperature. Basal body temperature is the lowest body temperature in 24 hours. Using a thermometer, you can keep track of changes in your basal temperature. Before ovulation, BBT, as a rule, falls, and immediately after ovulation, it rises sharply.
  2. Cervical mucus monitoring. Cervical mucus is a discharge that can be found on underwear for a month. For most of the cycle, these secretions are thick and sticky, but during ovulation, they can become thinner and more stringy. Their number at this time also, as a rule, increases.
  3. Track changes in the cervix. At ovulation, it becomes softer, moister and more open. You can notice this by inserting your fingers into the vagina and feeling for the cervix. This sign is more difficult to observe and usually requires some practice.

Ovulation often causes other symptoms that you may notice:

  • breast tenderness;
  • abdominal discomfort;
  • increased sexual desire.

Doctors are increasingly using ultrasound (ultrasound) to determine ovulation. Check with your doctor if you can use this method.

You may find it useful to add your symptoms and feelings to our application. This way you can see patterns in your cycle.

This is very simple but gives very accurate predictions. Confirmation of something is that more and more women are getting pregnant with Flo.

Women who ovulate at the end of their cycle report that their attempts to get pregnant may not be successful. Even if you know about late ovulation, it is difficult to predict when sex is most likely to lead to conception. Many women lose heart, especially if they know that friends or relatives have conceived without any problems.

First of all, don’t get discouraged! Millions of women around the world ovulate late but still manage to conceive. Focus on what to do to increase your chances of getting pregnant. The simplest, yet most important thing you can do is watch your cycle. The better you understand it, the easier it will be for you to determine when you are (or are about to) ovulate.

Once the egg is released from the ovary, it begins its journey down the fallopian tube to the uterus. From that moment on, she has 12–24 hours to be fertilized with sperm. Not much time at first glance. However, remember: spermatozoa can live in your fallopian tubes for up to 5 days. Therefore, if you had sex a few days before ovulation, the chances of fertilizing an egg are still high.

When planning a pregnancy with your partner, keep in mind methods that will help increase your chances of conceiving.

  • Tracking changes in cervical mucus. Get in the habit of watching the nature of your secretions. Before ovulation, you may notice that the amount of discharge has increased. In addition, they can become stretchy: you can probably stretch them up to a few centimeters between two fingers. All this points to the approach of ovulation — it’s time for intimacy with a partner! Immediately after ovulation, cervical mucus becomes thicker and cloudier, and its amount decreases.
  • Observation of changes in the cervix. Practice getting to know her by inserting your finger into the vagina while sitting on the toilet or squatting. But remember: hands should be clean and nails short! For most of the cycle, the cervix is ​​hard, dry, and closed. As ovulation approaches, you will feel it getting softer, wetter, and more open.
  • Ovulation tests. Using home tests to determine fertile days is quite effective. You can read more about this in the article The Complete Guide to Ovulation Tests.

Late ovulation may affect the ability to conceive. With an irregular cycle, it can be more difficult to track and predict ovulation. This makes it harder to predict when sex is more likely to result in conception.

If you have any of the conditions or symptoms described above, talk to your doctor. The doctor will talk about possible treatment options, and possibly lifestyle changes to improve your fertility and health.

By alexxlab

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