We are so happy you’ve found your way to us. Maybe you’ve just seen two lines on the pregnancy test, maybe a little life is already growing in your belly, or maybe you’re dreaming that it will happen soon. One thing is certain: you are in good and 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 focused specifically 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 an ultrasound. That way you can easily follow your pregnancy week by week and get a caring 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 very basic — but to answer them they require one thing: that you know your due date. That's why we've made it easy for you, if you don't already know it, with this due date calculator. Just enter the relevant information and we'll find 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 of becoming a parent can give a flutter in the 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 almost always concerns 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 helpful and widely used digital tools for expectant parents. Many people, especially at first, feel a strong need to calculate, compare and double-check the due date, and that's not surprising. Knowing when the birth is expected makes the waiting time both shorter and more tangible.
Let's dive into the different ways a due date can be calculated, and why these calculations have become so indispensable on the road to growing your family.
Starting point: Last menstrual period
Most due date calculators use the first day of the woman's last menstrual period as the starting point. That means that if you can precisely remember when your cycle last began, you're in a very strong position. The first day of the last period is regarded as pregnancy week 0+0 — even though fertilization itself typically occurs about two weeks later.
It may sound a little backwards, but the explanation lies in the body: ovulation — and therefore the possibility of fertilization — occurs around the midpoint of the menstrual cycle, often on day 14 in an average 28-day cycle. Because it can be difficult for most people to say exactly when fertilization took place, healthcare professionals always choose to calculate from the start of the period.
By adding 280 days — or 40 weeks — to that day, you arrive at the estimated due date.
Ovulation or fertilization as a 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, 38 weeks are added to the ovulation or fertilization day. The reason is that the two 'extra' weeks only apply when calculating the 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?
The due date is the estimated date when your baby is expected to be born. However, babies rarely follow a strict timetable, so treat your due date as a guideline — not a definitive answer. Most births occur between weeks 37 and 42 of pregnancy.
How is the due date calculated?
Even though it can easily be worked out with a calendar and a bit of math, there's still something very special about using an online due date calculator. It's fast, efficient, and very concrete. The visual element also helps make it all feel more real.
Most due date calculators ask for the following:
- The first day of your last menstrual period
- Alternatively: date of ovulation or conception
- Cycle length (especially if it differs from the standard 28 days)
When 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 waiting becomes concrete and easier to relate to.
It can feel as if the pregnancy already has day one recorded in the system, and it often brings joy, anticipation, and not least imagination. Even now, thoughts can wander 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 actually a kind of guesswork — albeit a fairly informed 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, deliver within a couple of weeks around the expected day, and that's precisely because the body and the baby themselves 'decide' when the time is right.
List of factors that can influence when labor begins:
- Genetic factors (family tendency)
- How many children you've had previously
- Specific conditions during pregnancy (e.g., too much or too little amniotic fluid)
- The 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 fixed contract.
However, if you know the date of your ovulation, the due date calculation can be even more precise. Fertilization 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 from the date of intercourse, you still need to know the timing of ovulation, as fertilization occurs shortly after. 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.
Already at the first doctor’s appointment or scan, many pregnant women report the first day of their last menstrual period. The doctor or midwife records it all in the medical record 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 expected due date can sometimes be adjusted. If the fetus turns out to be slightly larger or smaller than the 'schedule' indicates, a new due date is given.
Of course it can feel confusing if you thought you had the date under control. But ultrasound measurements provide a picture of exactly how far along the baby is in development, and therefore many are given a newly stated due date in connection with the nuchal translucency scan — and that is the date you should consider the most accurate.
Why does the due date feel so important?
The joy of anticipation can be hard to hold onto amid nausea and fatigue, but having a due date is something many expectant parents return to again and again. It frames the family's plans for the coming period.
The due date is often the first day noted in the calendar — and it's the one family, friends and even employers ask about.
The time leading up to the big day is spent on:
- Planning parental leave and holidays
- Setting up the nursery
- Buying practical items and creating wish lists
- Preparing mentally and perhaps physically for the birth
Because the baby almost never arrives exactly on that day, the wait becomes 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. Every time the calendar moves a week forward, 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 sense 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 ongoing focus on dates, weeks and days is that it actually makes 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 arrive.
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 menstrual period.
Many people think you are 0 weeks and 0 days pregnant at the moment of conception – but pregnancy is not actually counted that way.
Fertilization typically occurs about 14 days after the first day of your last period. That means you are often around 4 weeks along when your period is late and you find out you are pregnant.
Which week am I in?
You can calculate your pregnancy week from your due date using a week-by-week calculator, which — like a due date calculator — is based on 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. Being in week 12, for example, corresponds to having been pregnant for a full 11 weeks plus 1 to 6 days.
The method with 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’s more common to say: "I’m in week 12."
Our due date calculator can help you figure out exactly which week you are in.
When is my due date?
Most women give birth around week 40, but anything between 37+0 and 41+5 is considered completely normal. So if your due date falls on a particular day, there's no need to worry in advance — labour can just as well happen before or after.
A large study from the University of London shows that many women give birth at night or early in the morning. Seen from an evolutionary perspective this makes sense: it's generally quieter then, 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 your birth, which we recommend you read.
We also recommend the five stages of labour that you should know, so you won't be surprised when labour begins.
How long is a pregnancy?
A pregnancy lasts about 40 weeks, which we commonly call 9 months, and is divided into three trimesters. This counts the time from the last menstrual period. If measured from conception, a pregnancy lasts about 38 weeks (266 days).
Which week is the due date?
Your due date falls in week 40 of pregnancy. 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 actually a little longer, about 4.3 weeks.
Pregnancy trimesters
To make it easier to follow the development of your body and your baby, pregnancy is divided into three trimesters. Each trimester has its own changes and milestones. Read more about each trimester here.
First trimester
1st month: weeks 1–4
2nd month: weeks 5–8
3rd month: weeks 9–13
Second trimester
4th month: weeks 14–17
5th month: weeks 18–22
6th month: weeks 23–27
Third trimester
5th month: weeks 28-31
6th month: weeks 32-35
7th month: 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, as long as both you and the baby are doing well. When you reach 41+0, you are offered extra monitoring, and it is generally recommended to induce labor before 42 completed weeks.
At these check-ups the midwife or doctor monitors the baby's well-being, movements, heart rate, and the amount of amniotic fluid.
Being born after week 40 is rarely harmful, but there may be an increased risk of reduced amniotic fluid or oxygen deficiency 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 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 their due date)
- Hereditary factors on your mother's side
- The due date has been estimated imprecisely
- 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 had previous births 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 the 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.