Due Date Calculator

Once you have calculated your due date, you can also sign up for our newsletter and follow your pregnancy week by week with guides and information on what is happening in your body and with your baby. You can also use our due date calculator here.

What is a due date?

The due date is the estimated date when the baby is expected to be born. A pregnancy lasts on average about 40 weeks (280 days), and the due date is therefore typically calculated from the first day of your last menstrual period. Although the due date provides a good guideline, it is important to remember that babies rarely follow a calendar. Many babies are born both before and after the estimated date. The due date should therefore primarily be seen as a guiding time point that helps doctors and midwives monitor the progression of the pregnancy.

When is my due date?

To find out your due date, one usually starts from the first day of your last menstrual period. From this date, 40 weeks are added. This can seem a bit confusing because actual fertilization often only occurs about two weeks later during ovulation. Therefore, many will already be around 4 weeks pregnant when they discover they are pregnant. If you want to understand more about fertility and your cycle, you can also read our guide to ovulation and fertility.

How is the due date calculated?

The most common method for calculating the due date is called Naegele's rule. It is based on:

• the first day of the last menstrual period
• an average cycle of 28 days
• a pregnancy duration of 40 weeks

Due date calculators – like the one you find at the top of the page – use this method to provide an estimate of your due date. Later in the pregnancy, the due date may be adjusted during an ultrasound scan, where the size of the fetus is measured.

Calculate due date based on ovulation

If you know the time of your ovulation, the due date can also be calculated from this date. This method assumes that fertilization typically occurs within 24 hours of ovulation, and then 38 weeks (266 days) are added. This method can be more accurate if you have:

• closely monitored your cycle
• used ovulation tests
• undergone fertility treatment

Due date calculation for fertility treatment

If you become pregnant after fertility treatment, the due date can often be calculated more precisely because the time of fertilization is known. For example, with:

• IVF (in vitro fertilization)
• insemination (IUI)

the calculation is based on the date of fertilization or embryo transfer.

How far along am I?

Once you know your due date, you can also find out which week of pregnancy you are in. Pregnancy is usually divided into three trimesters:

• First trimester: Week 1 – 13
• Second trimester: Week 14 – 27
• Third trimester: Week 28 – 40

Many find it exciting to follow the development throughout pregnancy. If you want to know more about what happens week by week, you can read our week-by-week pregnancy guide.

How many babies are born on their due date?

Although the due date plays a big role at the beginning of pregnancy, only 4-5% of all babies are actually born exactly on their due date. Most births occur within the period of week 37 to week 42. Many babies are born a few days after their due date, but both earlier and later births are completely normal.

How long can you go past your due date?

If labor has not started around the due date, many will begin to wonder how long they can go past their due date. In Denmark, you will typically be offered extra check-ups around week 41, where monitoring will include:

• the baby's movements
• the baby's heart rate
• the amount of amniotic fluid

If the pregnancy continues for too long, induction of labor will often be offered before week 42. This means that the vast majority of births occur before then.

Signs that labor is approaching

Although the due date is a good guideline, labor rarely starts precisely on that day. Many experience signs in the days or weeks leading up to labor, such as:

• Braxton Hicks contractions
• the mucus plug coming away
• pressure in the pelvis
• early contractions

If you want to know more about the body's signals, you can read our article about signs of labor.

Follow your pregnancy towards the due date

Knowing your due date provides an overview of your pregnancy, but it is primarily the start of an exciting journey. Many find it reassuring to be able to follow what is happening in their body and with their baby throughout the pregnancy. When you calculate your due date, you can also sign up for our newsletter and receive guides, knowledge, and inspiration for pregnancy, childbirth, and the time after.

Frequently asked questions about due dates

What does due date mean in a pregnancy? The due date is the estimated date when the baby is expected to be born. It is typically calculated from the first day of the last menstrual period and is used as a guiding date throughout pregnancy.

How many weeks is a pregnancy in total? A pregnancy lasts an average of 40 weeks, which is approximately 9 months.

When is pregnancy counted from? Pregnancy is counted from the first day of the last menstrual period, even though fertilization typically occurs about two weeks later during ovulation.

How many days does a pregnancy last? A pregnancy lasts on average about 280 days when counted from the last menstrual period.

When is a baby considered born at term? A baby is usually considered born at term if the birth occurs between week 37 and week 42.

When is a pregnancy considered post-term? A pregnancy is called post-term if it continues beyond 42 full weeks.

What happens if you go past your due date? If labor has not started around the due date, you will often be offered extra check-ups where doctors or midwives monitor the baby's well-being.

Can you give birth before your due date? Yes. Many babies are born before their due date. Births from week 37 onwards are normally considered full-term births. Here you can read more about pregnancy discomforts.

Why do some pregnant women go past their due date? There can be several reasons, including genetic factors, being a first pregnancy, or the due date being calculated slightly incorrectly.

Is it normal to go past your due date with your first child? Yes, first-time mothers have a slightly higher probability of going past their due date than women who have previously given birth.

When is labor induction offered? In Denmark, many are offered induction if the pregnancy approaches 42 weeks.

Can the due date be calculated incorrectly? Yes, it can happen. If the menstrual cycle has been irregular, the due date may be adjusted during a scan.

What is the difference between gestational age and due date? Gestational age is the total length of the pregnancy measured in weeks and days, while the due date is the expected birth date.

When are you considered full-term? Many use the term "full-term" from around week 37, when labor can start at any time.

When can you feel life in your belly? Most people start feeling the baby's movements around week 18 to 22, but it can vary.

Can you influence when labor starts? There are many tips and myths about inducing labor, but labor usually only starts when the body and baby are ready.

How many babies are born before week 40? A large proportion of pregnant women give birth before week 40, but still within the normal range of between week 37 and week 40.

What do pregnancy weeks like 12+3 mean? When pregnancy weeks are written as 12+3, it means that you are 12 weeks and 3 days into the pregnancy.

When is pregnancy counted in months? Pregnancy is often divided into nine months, but healthcare professionals usually use weeks and days to describe the duration of pregnancy.

Can you give birth several weeks before your due date? Yes. Some babies are born several weeks before their due date, and in some cases, extra monitoring or treatment may be necessary.