Were so glad youve found your way to us. Maybe youve just seen two lines on a pregnancy test, maybe a little life is already growing in your belly, or maybe youre dreaming that it will happen soon. One thing is certain: you are in good, safe hands here. Cana Buttenschøn (Founder of Cana Care) is a trained midwife, has written five bestselling books for pregnant women and mothers, and has developed skincare products specifically focused on the pregnant body and the postpartum period.
When is your due date?
On this page, you can easily calculate your due date. Our due date calculator helps you determine your due date based on your last menstrual period, ovulation, or ultrasound scan. That way you can easily follow your pregnancy week by week and get a gentle overview of when you can expect to meet your baby.
It's often the first thing people are asked. Or "How far along are you in your pregnancy?" Questions that may seem completely basic — but to answer them they require one thing: that you know your due date. That's why we've made it simple for you, if you don't already know it, with this due date calculator. Simply enter the relevant information and we'll figure out when your baby is expected to make their arrival.
Calculate your due date
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It's perfectly normal to have a thousand thoughts and questions when you're expecting. Remember that, whatever the calculator shows, you're already well on your way — and we're here with advice, care and inspiration for the whole journey.
Understand the due date calculator
Thoughts about becoming a parent can give a flutter in your stomach that feels both exhilarating and frightening. From the moment two lines appear on the test, questions come flooding in. One of the very first is almost always about when the little one is actually expected to land in your arms. This is where due date calculation comes in.
A due date calculator is one of the most valuable and widely used digital tools for expectant parents. Many, especially at the start, feel a strong need to calculate, compare, and double-check the due date, and that's actually not surprising. Knowing when the birth is expected makes the wait both shorter and more tangible.
Let's dive into the different ways a due date can be calculated, and why these calculators have become so indispensable on the path to growing your family.
Starting point: last menstrual period
The vast majority of due date calculators start from the first day of the woman's last menstrual period. That means if you can precisely remember when your cycle last began, you're in a strong position. The first day of the last period is considered pregnancy week 0+0 – even though actual fertilization typically occurs about two weeks later.
It may sound a bit backwards, but the explanation lies in the body: ovulation—and thus the chance of fertilization—occurs around the middle of the menstrual cycle, often on day 14 in an average 28-day cycle. Because most people find it difficult to say exactly when fertilization occurred, healthcare professionals always choose to calculate from the start of the period.
By adding 280 days—or 40 weeks—to this day, you arrive at the estimated due date.
Ovulation or fertilization as the starting point
Some women have very precise knowledge of when ovulation occurred—possibly because they were closely monitored during a fertility treatment. If the day of fertilization is known, the due date calculation can become even more accurate.
Typically, you add 38 weeks to the day of ovulation or fertilization. The reason is that the two 'extra' weeks only apply when calculating a due date from the start of the last period.
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Everything you need to know about due dates and due date calculation
What is the due date?
Your due date is the estimated date when your baby is expected to be born. However, babies rarely follow a fixed schedule, so consider your due date a guideline — not a certainty. Most babies are born between weeks 37 and 42 of pregnancy.
How is the due date calculated?
Although it can easily be worked out with a calendar and a bit of math, there is still something special about using an online due date calculator. It’s quick, efficient and very concrete. The visual element also helps make it feel more real.
Most due date calculators ask for the following:
- First day of your last menstrual period
- Alternatively: Date of ovulation or conception
- Cycle length (especially if it differs from the typical 28 days)
Once the information is entered, you’ll quickly get a due date – and often even an overview of how far along you are, week by week. Suddenly the wait becomes tangible and easier to relate to.
It can feel as if the pregnancy has already been given day one in the system, and that often brings joy, anticipation and, not least, imagination. Already you may find your thoughts drifting to all the first clothes, the upcoming name, and what it will be like to meet a new little person.
Due date calculation based on ovulation
The whole due-date thing is really a kind of guessing game — albeit a fairly educated one. As you know, nature can be a bit less predictable than an app or a calendar.
Statistics show that only 3–5% actually give birth on the calculated due date. The vast majority, however, give birth within a couple of weeks around the expected day, and that's because the body and the baby themselves 'decide' when the time is right.
List of factors that can influence when labor starts:
- Genetic factors (family tendency)
- How many children you've previously had
- Specific conditions during pregnancy (e.g., too much or too little amniotic fluid)
- Exact timing of conception
- The baby's size and development
Although due-date calculators provide a very good estimate, they are best used as a guideline — not a strict contract.
If you do know the date of your ovulation, the due-date calculation can be even more precise. Conception typically occurs within 24 hours after ovulation, and in that case you add 38 weeks to the ovulation date.
Due date calculation based on intercourse
If you want to calculate the due date based on the date of intercourse, you still need to know the timing of ovulation, since fertilization occurs shortly afterwards. However, sperm can survive in the uterus for up to 3-5 days, so intercourse in the days leading up to ovulation can also result in pregnancy.
Due date calculation for fertility treatment
If you become pregnant via IVF, ICSI or insemination, the calculation starts from the date of fertilization and 38 weeks are added. This applies to both in vitro fertilization and insemination.
Doctor appointments and scans can change your due date estimate.
At the first doctor's appointment or scan, many pregnant women already report the first day of their last menstrual period. The doctor or midwife records it all in the file and continues the follow-up schedule from there.
But at the nuchal translucency scan in weeks 11–14 the baby's size is measured, and the actual due date can sometimes be adjusted. If the fetus turns out to have grown slightly larger or smaller than the 'schedule' indicates, you will be given a new due date.
Of course this can feel confusing if you thought you had the date under control. But ultrasound measurements give a clear picture of exactly how far along the baby is in its development, so many pregnant women are given an updated due date in connection with the nuchal translucency scan — and that is the date regarded as the most accurate.
Why does the due date feel so important?
The joy of anticipation can be hard to hold onto amid nausea and tiredness, but having a due date is something many expectant parents return to again and again. It frames the family's plans for the weeks ahead.
The due date is often the first day noted in the calendar — and it's the date family, friends and even employers ask about.
The time leading up to the big day is spent on:
- Planning maternity leave and holidays
- Setting up the nursery
- Buying practical items and making wish lists
- Preparing mentally and, perhaps, physically for the birth
Because the baby almost never arrives exactly on that day, the waiting can feel a bit like having Christmas Eve on a timetable where the date can shift. It's both beautiful, frustrating and quite magical.
The due date calculator's role in creating a sense of security
Dates are something most people find comfort in. Even when it's only an approximate date. Each time the calendar moves forward a week, it feels like a small milestone, and the waiting gains structure.
For many expectant parents, knowing the expected due date becomes a source of motivation throughout the months of pregnancy. It reminds you what it’s all about — and gives you the energy to get through the difficult or long days.
The feeling that a digital calculator can put a number to something so big also makes it easier to talk with others about what’s going to happen. 'It will be around June 15,' you suddenly answer when the curious ask. It creates a sense of togetherness and makes dreams about the future feel very present.
At the same time, it’s reassuring to know you can check a due date calculator whenever you need to calculate and confirm once more — just to be sure.
One of the loveliest things about due date calculation and the constant focus on dates, weeks, and days is that it actually allows room for both certainty and wonder. Pregnancy raises questions, builds anticipation, and opens up a love that grows with every week that passes. No matter when the little one actually chooses to make an appearance.
When is my due date?
Your due date is 40 weeks (280 days) after the first day of your last menstrual period, or 38 weeks (266 days) after ovulation or fertilization. It is completely normal for the due date to be adjusted along the way if a scan shows the baby is larger or smaller than expected. Learn more about your due date system here.
If your menstrual cycle is irregular, or for other reasons you do not know the start date of your most recent bleeding, an early ultrasound scan can be used to establish your due date. Any adjustment to the due date is usually made in connection with the nuchal translucency scan around week 12.
How far along am I?
Do you also enjoy following your baby’s development week by week? A pregnancy calendar can help you get an overview of how far along you are. As with calculating the due date, the starting point is the first day of bleeding of your most recent period.
Many people think you're 0 weeks and 0 days pregnant at the exact moment of conception — but pregnancy isn't actually counted that way.
Conception typically occurs about 14 days after the first day of your last menstrual period. That means you're often around 4 weeks along when your period is late and you find out you're pregnant.
Which week am I in?
You can calculate your pregnancy week based on your due date using a week-by-week calculator that — like a due date calculator — starts from the first day of your last menstrual period. If you know the timing of your ovulation, you can also use that to calculate the so-called gestational age.
There are, in fact, two ways to count pregnancy weeks. For example, being in week 12 corresponds to having been pregnant for a full 11 weeks plus 1 to 6 days.
The method using full weeks and days is used in the maternity record, where it might, for example, be written as 11+3. In everyday speech, however, it is more common to say: 'I am in week 12.'
Our due date calculator can help you determine exactly which week you are in.
When is my due date?
Most births occur around week 40, but anything between 37+0 and 41+5 is considered completely normal. If your due date falls on a particular day, you don't need to worry in advance — labor can easily happen both before and after.
A large study from the University of London shows that many women give birth at night or in the early morning. From an evolutionary perspective this makes sense: it's the quietest time, and the body has the best conditions to work undisturbed.
To help you on your way, we've written an article with five tips to prepare for childbirth that we recommend you read.
We also recommend the five stages of labor you should know, so you won't be surprised when labor begins.
How long is a pregnancy?
A pregnancy lasts about 40 weeks, which we commonly call 9 months and divide into three trimesters. This time is counted from the last menstrual period. If measured from actual fertilization, pregnancy lasts about 38 weeks (266 days).
Which week is the due date?
Your due date falls in pregnancy week 40. If the first day of bleeding in your last menstrual period fell on a Thursday, your due date will typically also fall on a Thursday – 40 weeks later.
The reason 40 weeks becomes 9 months is that a month is not exactly 4 weeks. Most months are a bit longer, about 4.3 weeks.
Pregnancy trimesters
To make it easier to follow your body's and your baby's development, pregnancy is divided into three trimesters. Each trimester has its own changes and milestones. Read more about each trimester here.
First trimester
Month 1: weeks 1–4
Month 2: weeks 5–8
Month 3: weeks 9–13
Second trimester
Month 4: weeks 14–17
Month 5: weeks 18–22
Month 6: weeks 23–27
Third trimester
Month 5: weeks 28-31
Month 6: weeks 32-35
Month 7: weeks 36-40
How many deliver on their due date?
Only about 4–5% give birth on the actual due date. The due date should therefore be seen more as a guideline than an exact date. In Denmark most babies are born around 40 weeks and 2 days, i.e., immediately after the due date.
How long before the due date is a cesarean usually performed?
The timing of a planned cesarean section depends on the reason. If neither the mother nor the baby is at risk, the procedure is usually scheduled as close to the due date as possible.
How far past the due date can you go?
As a rule, it is safe to go a few days past your due date, provided both you and the baby are doing well. When you reach 41+0 weeks, you will be offered extra monitoring, and it is generally recommended to induce labor before 42 completed weeks.
During these check-ups the midwife or doctor will monitor the baby's well-being, movements, heart rate and the amount of amniotic fluid.
Being born after week 40 is rarely harmful, but there can be an increased risk of reduced amniotic fluid or oxygen deprivation during labor, so you will be monitored more closely.
Why go past your due date?
Going past the due date is a natural variation in pregnancy length. There appears to be a hereditary component, and if you have previously gone past your due date, the likelihood is greater that it will happen again.
Who goes past their due date?
There are many myths, but little evidence suggests that the baby's sex or your age makes a difference. Research instead points to these factors:
- It is your first baby (about 28% go past the due date)
- Family history on your mother's side
- The due date has been estimated inaccurately
- Severe obesity
- You have previously gone past your due date
Who gives birth before their due date?
Pregnant women carrying multiples often give birth before 37 weeks. Women who have previously given birth may also tend to deliver slightly earlier. In addition, stress, smoking, and certain medical conditions can play a role.
In some cases, labor is induced early for the sake of the mother or baby.
Due date for twins
If you are expecting twins, pregnancy rarely lasts beyond 38 weeks. Many hospitals recommend induction around week 38 if labor has not already started, to ensure the best conditions for both babies.