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Due date calculator for conception day
Calculate your due date: How to find your baby's due date
Choose a calculation method Last periodConception dateI know my due date
First day of my last period
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.
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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Due Date Calculator — Amazingly Accurate Pregnancy Calculator
First day of your
Please choose the day your most recent period started.
Conception is approximately two days after intercourse.
Already know your due date? Click here
Pregnancy Week by Week Universal Header
Pregnancy due date calculator video
Learn how to calculator your pregnancy due date in this video.
When is my baby’s due date?
So you got your positive pregnancy test, you’re feeling some early signs of pregnancy, and now you’re wondering, “when is my baby’s due date?” We’ve got you covered with the Mama Natural due date calculator!
Enter your information in the due date calculator above and discover the best estimate for when your little bundle of joy will make his or her appearance.
How does this due date calculator work?
Because you may not know exactly when you ovulated or conceived, a due date calculator will typically calculate your estimated due date based on your last menstrual period (LMP).
Our online due date calculator uses a simple method to calculate your due date.
Your due date is estimated to be 40 weeks after the first day of your LMP
Your cycle is assumed to be 28 days long, with ovulation occurring at day 14
Therefore the calculator adds 280 days (40 weeks) to your LMP
This method of due date calculation is known as Naegele’s rule (more info on this below).
Due date calculator quote Our standard due date calculator adds 280 days (40 weeks) to the date of your last menstrual period (LMP)
My cycle isn’t 28 days. Will this due date calculator work for me?
Yes. The logic behind our pregnancy calculator works as follows:
The average cycle length is 28 days
If your cycle length is shorter, your due date will be earlier
For every day your cycle is shorter, your due date moves one day earlier
Similarly, if your cycle is longer, your due date will be later
For every day your cycle is longer, your due date moves one day later
What is the date of conception due date calculator illustration
How do you calculate due date from conception?
If you know when you conceived, our pregnancy calculator calculates your due date by adding 38 weeks to the date of conception. This method of calculation may be more accurate than a LMP due date calculation if you have irregular or consistently longer or shorter cycles than 28 days.
is the date of conception?
The date of conception is the day that the egg and sperm meet.
Women who track their ovulation may know their exact date of conception. But for many women, date of conception can be tricky to pinpoint.
Sperm can live in a woman’s body for up to five days, and the ovum (egg) can live for up to 24 hours after being released. In other words, you have a six-day window where you could potentially get pregnant each month.
Do you already know your due date but want to know when you likely conceived? Try our reverse due date calculator.
What is an estimated due date (EDD)?
An estimated due date (EDD) is a “best guess” as to when baby might be born based on a due date calculator like this one.
However, only 4% of babies are born on their due date! Whereas 80% of babies are born within the window of two weeks before and two weeks after your due date calculator results. (See “due month” section below.)
Baby due date on a calendar with pregnant woman background – only 4% of babies are born on their due date
What is “gestational age?” Can it be different than what the calculator shows?
Gestational age (GA) is the term used to describe how far along the pregnancy is and how long baby has been gestating (growing in the uterus).
If you get an ultrasound you may notice a “GA” on the image with a number of weeks and days. This figure is based on how the baby is measuring, not on your LMP, which the due date calculator uses.
It’s normal for these dates to not match up perfectly. If there are significant differences in the dates, your doctor may want to dig deeper to determine conception date. As a result, your midwife or doctor may change your due date based on the ultrasound gestational age.
Early ultrasounds are very accurate when dating a pregnancy and can be helpful if you don’t know your LMP or your periods are irregular.
Note that you don’t have to have an early ultrasound, especially if you are fairly certain of your cycle length and conception window. This study shows that early dating ultrasounds don’t change the incidence of induction.
How are the weeks of pregnancy calculated?
The 40 weeks of pregnancy begin on the first day of your last menstrual period.
This can be a little confusing because, for most people, conception doesn’t occur until day 14 of the menstrual cycle. So yes, you aren’t actually pregnant during those first two weeks of pregnancy.
Here’s a more in-depth answer to that perennial question of How many weeks pregnant am I?
What is a
A “due month” is a more accurate timeframe for when you can expect to deliver your baby. Only 4% of babies are born on their due date. Whereas 80% of babies arrive either two weeks before the due date or two weeks after. Hence the term “due month.”
The length of a natural pregnancy can vary by as much as five weeks. (source)
A due month helps some mamas reduce the stress and fear of going past their due date.
To calculate your due month, simply subtract two weeks from your EDD given by your practitioner or our due date calculator and also add two weeks to your EDD. Voilà, your due month!
Yet another way to handle this tricky business of calculating your pregnancy calendar is to add two weeks to the end of your EDD and say, “Baby will be here before [that date].”
What is Naegele’s rule for due date calculation?
Naegele’s rule is what this due date calculator and pregnancy calendar is based on. Named after a German Obstetrician who practiced in the early 1800’s, Naegele’s rule predicts childbirth to occur 280 days afterthe first day of the last menstrual period.
However, Naegele’s rule assumes that your cycle is 28 days long with ovulation occurring on day 14, which isn’t the case for many women. So other ways of calculating your due date may be more accurate.
(How accurate is your due date? Find out in this post.)
Modern data suggests that women have their babies a few days after their due date on average. Studies like this one found that Naegele’s rule consistently places the due date about 2-4 days too early. So a better estimate may be 40 weeks and 3 days from LMP.
Alternatively, you can use our Advanced Due Date Calculator, which uses the Mittendorf-Williams rule to calculate your due date, which has been shown to be more accurate.
Due date calculator quote 2 Modern data suggests that Naegele’s rule places the due date about 2-4 days too early
What’s the Mittendorf-Williams rule?
This study done in 1990 showed that pregnancy lasted an average of 288 days past LMP for Caucasian first-time moms. For Caucasian women who were notfirst-time moms, their date of delivery averaged 283 days past LMP (3 days after Naegele’s rule predicted). This finding is known as the Mittendorf-Williams rule.
While Naegele’s rule is still the most widely used formula for a due date calculator, the Mittendorf-Williams rule is proving to be more accurate. But it’s a much more complex calculation, taking into account:
Number of pregnancies
Average luteal phase length
Alcohol during pregnancy
Coffee during pregnancy
Our Advanced Due Date Calculator uses the Mittendorf-Williams rule.
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My Bestselling Natural Pregnancy Guide ?
Reverse Due Date Calculator ◀️
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Ready to calculate your due date?
First day of your
Please choose the day your most recent period started.
Conception is approximately two days after intercourse.
Already know your due date? Click here
Online calculator and pregnancy calendar
The online tool allows you to calculate the exact gestational age, the expected date of delivery and the day of maternity leave. The calculation is made by the date of the last menstruation, by the date of conception and by the expected date of delivery, and the result is displayed on an interactive calendar by weeks and trimesters with information about the child (height and weight) at each stage of pregnancy.
Online pregnancy calculator
Last menstrual period Due date Conception date
Weekly pregnancy calendar
Fetal growth cm
Fruit weight, gr
1st trimester of pregnancy
0.02 - 0.03
0. 04 - 0.1
0.4 - 0.5
0.1 - 0.16
0.5 - 0.8
0.3 - 0.6
0.9 - 1.3
0.6 - 1.2
1.3 - 1.7
1.3 - 2.4
1.7 - 2.1
2.1 - 3.2
2 - 4
3.3 - 4.3
4 - 6
2nd trimester of pregnancy
3rd trimester of pregnancy
Gestational age. Date of birth. Calculate gestational age and due date
What is a calculator?
How does a calculator work?
Other ways to determine and confirm the due date.
How accurate is the calculator?
What is a calculator?
In most cases, women do not know the exact date of conception, but they can with great certainty to say when the last menstrual cycle began. The first the day of the last menstruation is the starting point. Well, then 9 comes into play0014 pregnancy calculator - a program that makes a lot of calculations for you and answering almost all questions of interest to the expectant mother :
when was conception approximately;
what is the estimated date of delivery;
what is the exact week now and how much is left before the birth;
how a child develops, what size it is, what it already does in the womb and what skills it has.
Calculator free, always available online, easy to use, has concise and understandable interface, will not let you make arithmetic errors and displays results in a visual and interesting way. In addition, you can always check the accuracy calculator, independently making calculations according to well-known obstetric techniques, which we present below.
To calculate the gestational age and the expected date of delivery, a woman needs to enter in the calculator, only the date of the first day of the last menstruation (LPM) in the format "day month Year". If you enter the last day of your period or a known date conception, the calculator will show completely different results, you need to enter exactly the start date last menses.
The calculator calculates the obstetric period - this is when the first day of menstruation is considered like the first day of pregnancy. It is by obstetric term that gynecologists track the development fetus, prescribe tests and examinations.
The gestational age in the calculation results of the calculator is shown in weeks, this is the most simple and convenient interval. There are other generally accepted intervals for dividing such a large period - months (10 lunar months of 28 days) and trimesters. The trimesters divide the process intrauterine gestation into three phases of 13 weeks each.
The results display the exact period in weeks and days, a brief description of the development of the fetus, the height and weight for the calculated week are indicated, which organs are being formed, what can already be felt and do baby. A link is provided to the full article with colorful illustrations, telling about the condition of the fetus and mother, tests and examinations, recommended diet, possible problems and ways to overcome them. You will always know what to prepare for.
This calculation displays both fetal ages: the so-called "gestational" fetal age (menstrual), which is different from the so-called "ovulation" age (fertilization), it is two weeks less and is counted from the estimated date of conception. Therefore, all the details fetal development and well-being of women are considered from week to week, starting precisely from the third week.
In addition, you will know how many days are left before childbirth, under what sign of the zodiac and in what year of the Chinese calendar your baby will be born, by clicking on additional links you can determine the color of the eyes, the blood type of the child.
Depending on the week, additional links are displayed to calculators for checking ultrasound results, hCG hormone levels, blood test results, weight gain rates. If you wish, you can calculate an individual calendar of analyzes and examinations, both for mother and child.
Starting in the second or third trimester, you can find out about your benefits and calculate your benefits. amounts. For working mothers, it is possible to determine the date of maternity leave and find out if you are entitled to annual leave leave before the decree.
Whatever week you are, the calculator will offer you to test your knowledge using interactive tests "Care of a newborn", "Feeding of newborns", "Tests and examinations of pregnant women", "Rights of pregnant women". You will just have time to fill in the gaps and improve your knowledge on these important topics.
The calculator will also calculate the estimated date of conception of the child, according to which, using Chinese gender calendar, you can find out who you will be - a girl or a boy. According to the results of the ultrasound, it will be interesting to know whether the prediction came true.
How does a calculator work?
All calculations of our calculator are based on the obstetric calculation method, as the most accurate, scientifically based and universally accepted method for calculating gestational age. other methods, for example, a report from the day of intercourse or from ovulation cannot be considered reliably accurate due to the characteristics of the reproductive system.
The length of the cycle may differ for different women, one has 21 days, the other has 34, moreover, in the same woman, the cycle may be irregular and fluctuate in duration during years for various reasons. On average, most women have a menstrual cycle is 28 days.
But one thing is common to all: conception of a child is possible only during ovulation - if there is no mature egg, then conception will not occur.
At the beginning of the cycle, a follicle forms on the surface of the ovary, inside which the female matures. sex cell. In the middle of the cycle, the follicle sac ruptures under the influence of strictly defined hormones. and allows spermatozoa access to the oocyte.
After ovulation, the female gamete lives from 24 to 36 hours, at which time conception must occur, otherwise the cell dies. This process is repeated every cycle.
It turns out, regardless of the length of the cycle, nature allocates only one or two days for the process of conception. However, this does not mean that sexual intercourse can lead to pregnancy only during the hours when the oocyte lives. Not, due to the ability of spermatozoa to survive for a long time in the female body, sex even 3-4 days before release the egg can lead to fertilization immediately after its release from the follicle. With active sexual life in general it is impossible to determine whether sexual intercourse before, during or after ovulation led to conception.
Therefore, in obstetric practice, it is generally accepted that conception occurs during the period of ovulation - 14 days before before the end of the menstrual cycle. And again, we are faced with a harsh reality here - a woman ovulates can happen both earlier and later than the above day. Based on all this, it is customary to count from the date of the last menstruation, this is both easier, and the woman usually remembers this date.
Thus, according to the obstetric standard, the first day of the last menstruation is the first day pregnancy, and the day of conception falls approximately at the end of the second week. If a woman finds out about the delay, then this is already the 4th week and the gynecologist, regarding a week-long delay, is already setting a deadline of 5 weeks.
Our online calculator is based on this obstetric method. Weeks are normal calendar months, and obstetric months, each of them has exactly 4 calendar weeks.
Pregnancy lasts an average of 40 weeks or 10 obstetric months , in calendar days this is good well-known 9 months .
31 31 31 310039
and the fetus, each trimester has its own characteristics. For example, in the first trimester there is a rapid the formation and development of the organs of the child, then miscarriages most often occur. In the third trimester it is necessary to prepare for the manifestation of possible problems associated with pregnancy - hypertension, toxicosis.
There are 3 calendar months in one trimester, the first trimester is 1-13 weeks, the second trimester is 14-27 weeks, the third is 28-42 weeks .
or all three ways:
Add the average duration of pregnancy, which is 280 days, to the first day of the last menstruation.
Add 9calendar months to the first day of the last menstruation and subtract 7 days from the resulting date.
Subtract three months from the first day of your last period and add 7 days to the result.
Absolutely the same time is considered in the antenatal clinic, the same methods are used in round paper obstetric calendars.
Other ways to determine and confirm due date
There are no other scientific methods for determining gestational age and due date. But there are methods using which can be confirmed or corrected. Again, almost all of them are based on the obstetric method, statistical data and data from an objective examination of the expectant mother.
The main objective sign of pregnancy is an increase in the size of the uterus, which in the first months is determined by vaginal examination, and after the third - by the height of the fundus of the uterus. By the end 1st month (28 days) the uterus corresponds to the size of a chicken egg, 2nd month (56 days) - an average fist women, then each month has its own size. There is no need to talk about the accuracy of this method.
Additional information about the due date and due date can be obtained by measuring the length of the fetus. measurements produce a tazomer in the position of a woman lying on her back. One button of the tazomer is placed on the lower pole head, the second - at the bottom of the uterus. Calculations are made using a special formula, but the result is also approximate due to different assumptions, for example, the thickness of the abdominal walls can be taken in both 3 and 5 cm.
According to the level of hCG
At the earliest stages (from the 4th to the 8th week), pregnancy is confirmed by the level of hCG. By date of conception or, if it is unknown, then the obstetric period is determined from the first day of the last menstruation, and from it the hCG rate is determined. If the pregnancy is proceeding normally, then the hormone levels will correspond, or rather be within the range of valid values. The accuracy of this method is very low, as hormone levels are indicated in a wide range and the main thing for which this method is used is to determine the normal development fetus. The hCG level may not fall within acceptable limits, but if it doubles in two days, the fetus is considered to be developing normally. As you can see, this method is not always possible to use.
Ultrasound can also confirm pregnancy, this method is used to detect fetal egg and registration of heartbeats. Ultrasonography is currently the only method allowing with the greatest degree of accuracy to establish the gestational age and follow the development of the fetus, starting from the very first weeks of its intrauterine development.
The date of the last menstruation is entered into the ultrasound machine and, upon further scanning, the doctor determines how embryonic development corresponds to the obstetric term. Statistical tables of sizes are set in these devices fruit for each week and day.
In early pregnancy, when embryos develop at about the same rate, it is easier to compare their sizes are with average statistical norms and it is possible to more accurately determine the age. In this case, the doctor evaluates parameters of the baby, compares with the tables, gets the gestational age and, after adding two weeks, calculates obstetric term. If a woman did not remember the start date of the last menstruation, then the only way to determine the date pregnancy.
Later, when the fetus begins to develop according to its individual genetic program laid down by the parents (large or petite build, large or small height), it becomes more difficult to accurately determine the week.
In the middle of pregnancy, usually at 20 weeks in nulliparous women and at 18 weeks in multiparous women first fetal movement. Before the advent of ultrasound, this method was used without alternative to confirm the term pregnancy, there was no other way. Now this is an auxiliary method, it cannot be considered exact, since not everyone is able to recognize the first stirring. Currently no longer used for its intended purpose.
How accurate is the calculator?
The same as the calculator, the method of calculating the gestational age is used by an obstetrician-gynecologist in the women's consultations, in a hospital for conservation, in a maternity hospital, in medical equipment - ultrasound machines and laboratory equipment.