Calculate estimated due date pregnancy

Calculate your due date: How to find your baby's due date

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BabyCenter's Due Date Calculator

Use our pregnancy due date calculator by plugging in either the date of your last menstrual cycle or the date you know you conceived. The calculator will do the rest.

How is my due date calculated?

There are several ways your due date is determined. If you happen to know the day you conceived, you can count 38 weeks from that day to find your due date. (Human gestation takes about 38 weeks.)

But very few expectant moms know exactly when they conceived. Even if you only had sex once during your fertile period, you wouldn't conceive on that day unless you happen to be ovulating. Sperm can live for up to five days inside your fallopian tubes. So, it could be up to five days after you have sex that you release an egg (ovulate) and it gets fertilized by a waiting sperm. That's the day you conceive.

So, without knowing the day of conception, how does anyone determine a due date?

First day of your last period

The most common way to calculate your pregnancy due date is by counting 40 weeks from the first day of your last menstrual period (LMP). And that's how most healthcare providers do it.

If your menstrual cycle length is the average length (28-day cycle), your menstrual cycle probably started about two weeks before you conceived. This explains why pregnancies are said to last 40 weeks instead of 38 weeks.

This method doesn't take into account how long your menstrual cycle actually is or when you think you might have conceived. But generally speaking, women typically ovulate about two weeks after their menstrual cycle starts. And women are more likely to know when their last period started than the day they ovulated.

Conception date

If you do happen to know precisely when you conceived – say, if you were using an ovulation predictor kit or tracking your ovulation symptoms – you can calculate your pregnancy due date based on your conception date. Just choose that calculation method from the pulldown above and put in your date.

Note: Again, you don't necessarily conceive on the day you have sex.

IVF transfer date

If you conceived through IVF, you can calculate your due date using your IVF transfer date. If you had a Day 5 embryo transfer, count 261 days from your transfer date. If you had a Day 3 embryo transfer, count 263 days.

Can my due date change?

Your healthcare provider might revise your due date if your baby is measured during a first trimester ultrasound scan and found to be much bigger or smaller than expected for gestational age. This is more likely to happen if you have an irregular menstrual cycle length that makes it hard to pinpoint the date of conception.

Your healthcare provider will measure your baby during that ultrasound exam to figure out how far along your baby is and then provide you with a new due date.

What if I already know my due date?

If you already know your due date, you can use this calculator to see your pregnancy timeline. It will tell you when you'll hit various milestones, and when you may be due for prenatal tests and prenatal visits. You'll also find what your baby's sign and birthstone will probably be and which famous people were born on your due date.

How likely am I to give birth on my due date?

Of course, a due date calculation is always approximate, whether it's from our tool or from your doctor or midwife. Only 1 in 20 women delivers on their due date. You're just as likely to go into labor any day during the two weeks before or after.

Want more information about how the weeks, months, and trimesters of pregnancy are counted? See our pregnancy timing chart.

How soon can I take a pregnancy test?

With all this talk about pregnancy due dates, you may be wondering when you can take a pregnancy test. To ensure you get the most accurate reading, it's best to wait a few days after your missed period to take a pregnancy test.

At-home urine tests measure the amount of hCG (human Chorionic Gonadotropin) present in your body. If you take a pregnancy test before you miss your period, you may not get an accurate result, despite what some tests advertise.

If you're getting a blood test in your provider's office, you may get results sooner. These tests also measure the amount of hCG in your bloodstream, but they're more sensitive than at-home urine tests. Blood tests may be able to detect pregnancy six to eight days after ovulation.

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Pregnancy tests: How soon can you get a positive pregnancy test?

Pregnancy tests work by detecting the presence of a hormone called human chorionic gonadotropin (hCG) in your urine. Some home pregnancy tests claim they're sensitive enough to give a positive result as early as five days before you would expect your next period. But you're more likely to get an accurate result (and avoid a false negative pregnancy test) if you wait to test until after the first day of your missed period.

How soon can you take a pregnancy test?

You're more likely to get an accurate result if you wait a few days to a week after you expect your period before taking a pregnancy test.

Some home pregnancy tests claim they're sensitive enough to give you a positive result as early as five days before you would expect your next period. And some women will have produced enough hCG to get a positive result at that point. So if you're anxious to know, go ahead and try it. If you get a negative result, you can just wait and test again later if you still haven't gotten your period.

Most home pregnancy tests claim to be accurate on the day you miss your period, but even then, the amount of hCG in the urine at this time can vary a great deal from one woman to another.

If you test too soon, you may get a false negative pregnancy test (a negative result even if you are pregnant) or an unclear result like a faint line on a pregnancy test.

How do pregnancy tests work?

Home pregnancy tests tell if you're pregnant or not by detecting the presence of hCG in your urine.

This hormone is produced by cells that will develop into the placenta. It first enters your bloodstream when the fertilized egg starts to implant in the lining of your uterus, as early as six days after fertilization.

The amount of hCG in your body then increases rapidly over the next few weeks, often doubling every two days or so. When a pregnancy test detects the hormone in your urine, it shows a positive result.

Home pregnancy tests are now about 99 percent accurate, when done correctly. And there's no reason to pay more for one test over another. As long as a test isn't expired, it should be equally as accurate as another test.

What will differ between tests is their sensitivity. Detecting hCG in the urine of someone 6 months pregnant (when there's plenty of hCG) versus 6 days past ovulation (when there's a very small amount of hCG) are two very different tasks. The ability of a test to pick up small amounts of hCG in your urine depends on the sensitivity of the test.

It's not always easy to tell which tests are the most sensitive. New products come out frequently, and manufacturers can make improvements at any time.

But some package inserts provide information about a test's sensitivity – that is, they report the lowest concentration of hCG in milli-International Units per milliliter (mIU/ml) of urine that the test can detect. For example, a pregnancy test that claims to be able to detect hCG at 20 mIU/ml should be more sensitive than one that claims to detect it at 50 mIU/ml.

How do I use a home pregnancy test?

For best results when using a home pregnancy test:

Make sure the test is current. Check the expiration date on the package, especially if you've had it for a while. If you've been storing the test anywhere that gets moist or warm, like the bathroom, it may have deteriorated. If that's the case, it's better to throw it away and get a new one.
Test first thing in the morning. Your urine is most concentrated when you first get up, so hCG levels (if present) will be easier to detect at that time.
Read the directions carefully. Directions vary with different brands. Some require you to urinate in a cup and then use the dropper provided to place a small sample in the testing well. With others, you can pee directly onto the testing device. And some let you do either.

The tests also vary in how they display the results. For example, some show pink or blue lines on the test strip, while others reveal a red plus or minus sign in a window. "Digital" tests tell you in words whether you're pregnant. Most have a control indicator (often a second line or symbol) to indicate whether the test is valid.

It may take up to 10 minutes to see results. If the control indicator doesn't show up properly, the test may be faulty. If this happens, you can usually call the manufacturer and have them send you a new one (though it probably won't arrive soon enough to use that same month).

If you have questions about how to use a test, call the manufacturer's toll-free number on the package instructions.

If the test shows a negative or a faintly positive result, wait another few days or a week and try again if you still haven't gotten your period. One possibility is that you ovulated later in your cycle than you thought and took the test too early to get a positive result.

Don't assume that one negative result means you're not pregnant. The amount of hCG produced is different for every woman and varies with each pregnancy. If you suspect that you're pregnant (for instance, if you're having early pregnancy symptoms) and still have a negative test, repeat a urine pregnancy test in a week if you still haven't gotten your period.

If you still haven't gotten either your period or a positive result two weeks or so after you would expect it, contact your healthcare provider.

False positive pregnancy tests

A false positive pregnancy test means that you get a positive result, but aren't pregnant. These are uncommon, but they can happen under certain circumstances:

You had a miscarriage or a pregnancy termination in the previous eight weeks or have a molar pregnancy.
You've taken a fertility drug containing hCG (used to induce ovulation in fertility treatments).
You have a rare medical condition, such as an hCG-secreting tumor.
You're using an expired or faulty test.
You're experiencing menopause or perimenopause.

If you have an early positive result and then get your period soon after, you may have had what's sometimes called a chemical pregnancy. This means a fertilized egg implanted in your uterus and developed just enough to start producing hCG, but then stopped developing for some reason. This form of early pregnancy loss usually happens when the fertilized egg has defects that prevent it from growing normally.

After a chemical pregnancy, your period may be a little heavier and a few days later than usual.

Note: An ectopic pregnancy usually results in a positive pregnancy test, even though these pregnancies show slower hCG rises. No matter what result you get from a pregnancy test, call your healthcare provider right away if you:

Feel dizzy or faint.
Have abdominal pain (especially a sharp or stabbing pain in your abdomen or on one side of your pelvis).
Have abnormal bleeding.

Pregnancy blood tests

Most healthcare providers use a urine pregnancy test, just as you would at home – but your provider may use a blood test instead. It takes anywhere from an hour to a day or more to get the results.

There are two types of pregnancy blood tests:

A qualitative hCG blood test simply detects whether there is hCG in your blood. It will give pregnancy results at about the same time as a urine test. The results return as "positive" or "negative."
A quantitative blood test (beta hCG test or serum test) measures the exact amount of hCG in your blood. The results return as a number. This test is very accurate. It can detect hCG as early as six to eight days after ovulation, about a week before your period is due. It takes longer to get results from a quantitative blood test, though.

Some testing companies will let you pay online and then go to a lab and have a blood sample taken. The testing company will provide you with your result the next day by phone or online. These tests start at about $40. If you decide to use one of these companies rather than going through your healthcare provider, be sure to find out which type of blood test they're using.

What to do after a positive pregnancy test

Some women take more than one pregnancy test (or several) just to be sure – but that's not necessary. Once you've gotten a positive pregnancy test, call your healthcare provider to set up a prenatal visit or to discuss your options if you're uncertain about continuing the pregnancy.

For prenatal care, providers typically schedule the visit for when you're at least 8 weeks pregnant, but it varies. Some will see you sooner, particularly if you have a medical condition or have had problems with a pregnancy in the past. It's especially important to see a provider soon if you're having nausea and vomiting, vaginal bleeding, or abdominal pain.

If you don't already have a family doctor, ob-gyn, or midwife, do some research and ask for recommendations. But don't delay your care while searching for a good fit, because you can always switch providers later. At your first prenatal visit, your provider will take your health history, explain your options, and more.

Learn more:

I'm pregnant – now what?
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How to correctly calculate the gestational age and determine the date of delivery

It often comes as a surprise to first-time pregnant women that in obstetrics the gestational age is determined not in months, but in weeks. But the surprises do not end there - the fact is that the obstetric period is calculated not from conception, but from the first day of the last menstruation.

In fact, pregnancy occurs two weeks after the start of the obstetric period, at the time of ovulation, when the sperm meets the egg. Thus, the age of the embryo, or gestational age, differs from the obstetric one by 2 weeks down.

How long does pregnancy last?

The obstetric term of a term pregnancy is 40 weeks, or 280 days. It is on the basis of the obstetric gestational age that the doctor will prescribe tests and examinations for you, determine the date of maternity leave and calculate the EDD (estimated date of birth).

Doctors use the Negele formula to calculate the EDD. According to this formula, if we add nine months and seven days to the first day of the last menstruation, we get the estimated date of delivery.

Unfortunately, determining the gestational age from the first day of the last menstrual period is not a very accurate method. It is well suited for women with a stable 28-day cycle, but if your cycle is slightly longer or shorter, then the date of ovulation shifts, respectively, and the actual obstetric gestational age will differ from the established one.

The most accurate way to calculate the EDD is to add 266 days to the date of the last ovulation (if you know it).

How to confirm pregnancy, determine the duration of pregnancy and the date of delivery

By itself, a delay in the start of a new menstrual cycle does not necessarily indicate pregnancy - failures can be explained by diseases, excessive physical exertion or stress. Pregnancy must be confirmed with an hCG test or examination on a gynecological chair. 1) Blood test for hCG cycle or the woman will feel the first symptoms. Also, an analysis of the level of hCG in the blood allows you to determine the gestational age with an accuracy of about two weeks.

2) Home pregnancy test

Home pregnancy tests also work by measuring hCG levels, but they are less sensitive than blood tests. The most modern of them can not only confirm the presence of pregnancy a few days before the delay, but also indicate (not too accurately) an approximate date.

Tests of the old generation will show a more or less accurate result only after a delay, that is, after 2-4 weeks from conception.

3) Gynecological examination

A qualified gynecologist-obstetrician can diagnose pregnancy during an examination starting 3-4 weeks after conception, focusing on changes in the shape and size of the uterus, as well as other signs.

4) Ultrasound

Ultrasound is the most accurate way to diagnose pregnancy. With the help of ultrasound with a transvaginal sensor, it is possible to determine the presence of a fetal egg in the uterus already 1-2 weeks after conception (3-4 obstetric weeks), but fetal heartbeats can only be detected for a period of 5-6 obstetric weeks. It is possible to determine the gestational age with high accuracy (up to 2-3 days!) With the help of ultrasound only from 6-7 weeks.

If the delay, as well as the result of an hCG test or blood test, indicate that you will soon become a mother, do not rush to get an ultrasound right away. Wait another 2-3 weeks, then by ultrasound you will not only be accurately determined by the period, but will also be allowed to listen to the baby's heartbeat.

If you did not do an early ultrasound to confirm pregnancy, then for the first time you will encounter this study at the 10-14th week. At the same time, the exact gestational age and PDR will be established or corrected for you. During pregnancy, you will need to undergo such an examination at least twice more. This will happen at 20-24 and 30-34 weeks. However, it is worth saying that ultrasound in the 2nd and 3rd trimesters may have an error in determining the gestational age. The PDR established according to them may differ from the real one by 2-3 weeks. That is why it is so important not to miss the first screening and do an ultrasound on time.

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How to calculate the gestational age

Calculating the gestational age is not always such an easy task. Of course, if you know exactly when there was the only attempt to conceive a child, then you will not have any special problems with determining the gestational age, but even in this situation, not everything is clear. After all, pregnancy does not begin immediately after the end of sexual intercourse.

It is important to know the exact date of pregnancy because most of the procedures, tests and norms are strictly tied to certain cycles of the perinatal period.

How to determine the duration of pregnancy

It is important to understand that it is impossible to determine the day of pregnancy with 100% accuracy. Existing methods only help to minimize the error in determining the date. There are six popular techniques in service with obstetricians and gynecologists. Let's dwell on them in more detail.

Determination of the gestational age by the date of the last menstruation

The easiest way to determine the gestational age is to start from the date of the last menstruation. After a successful conception, the start of the next menstruation falls on the 4th week of pregnancy. This technique implies that a fertilized egg begins to divide even before ovulation. The method is used when calculating the obstetric gestational age and calculating the expected date of birth (PDR) using a special formula. This technique allows you to more or less accurately calculate the timing with a regular menstrual cycle. The gestational age calculated by the date of the last menstruation has an error of two weeks.

Calculation of the gestational age by the height of the uterine fundus

This method is extremely easy to use, therefore it is often used by obstetrician-gynecologists as an auxiliary. Using a ruler, the doctor measures the distance between the upper edge of the uterus (bottom) and the pubic joint. The size of the uterus in centimeters corresponds to the approximate gestational age in weeks.

Determination of the gestational age by the first movement of the fetus

This is not the most reliable method, so it is not worth focusing on it. However, it will not be superfluous to know that in nulliparous women, the baby begins to move at the 20th week, and those who give birth a second or more times, the first tremors are felt at the 16th week. True, there is a risk of confusing fetal movement, for example, with intestinal motility.

Ultrasound gestational age

Ultrasound can be a very effective tool for determining gestational age, but it must be done between 10 and 12 weeks. That is, in order to clarify the day the pregnancy began, you need to know at least approximately it. The doctor measures the fetus and calculates the date using a special formula. The error in determining the term using ultrasound at a later date increases, as the individual characteristics of the baby's development begin to manifest themselves strongly.

Calculation of the term by the date of conception

It should be said that the moment of conception is not formally the beginning of pregnancy. Distinguish embryonic gestational age and obstetric. As a rule, the obstetric period is more important for monitoring the development of the fetus. Usually, the moment of conception coincides with the date of ovulation. The disadvantage of this method is that the doctor cannot fully rely only on the data on the day of conception.

Gestational age and hCG

Pregnancy age can be determined by the level of human chorionic gonadotropin (hCG) in the blood of a pregnant woman. To do this, you need to donate blood from a vein. As a rule, this method is used in the very early stages, when a woman does not yet know for sure if she is pregnant. All popular pregnancy tests are based on the principle of determining the amount of hCG.