What is a term calculator?
A due date calculator shows the expected date of birth (due date) based on the date your last menstrual period started. The calculation is based on an average pregnancy length of 280 days (40 weeks). This is the same method that Danish maternity wards and scan clinics use as a starting point until a nuchal translucency or malformation scan possibly adjusts the date.
See also: Pregnancy test at a GP
How to use the calculator
- Select the first day of your last menstrual period on the calendar.
- Press “Calculate term”.
- Instantly see your expected due date, pregnancy week, and today's status (e.g., "You are in week 12 + 3").
The calculation is anonymous – we do not store any dates or personal information.
What does week xx + x mean?
The notation “week 12 + 3” means that the pregnancy has lasted 12 full weeks plus 3 extra days. The first number indicates the number of full, completed weeks, while the number after the plus sign shows how many days have elapsed beyond the full weeks.
The system makes it easy for healthcare professionals to indicate the fetus's exact age and the timing of examinations, because even a few days' difference can have an impact on scans, blood tests and assessment of development.
When are you going to give birth?
Although the due date provides a good guide, only about 4% of pregnant women give birth exactly on the estimated day. Most births occur in the window from 37 + 0 to 41 + 6 weeks, when the baby is considered full-term. Your baby ultimately determines the timing via complex hormonal signals that trigger contractions, and factors such as first-time birth, genetic predisposition and your own cycle length can shift the timing a few days to either side. If you go more than 41–42 weeks, the hospital will typically offer induction to reduce the risk of complications. So use the due date as a guide, but have your bag ready a few weeks before – and enjoy the peace and quiet for the final preparations while you wait for your baby to choose his or her perfect birthday.
Scientific background
The length of pregnancy is measured from the first day of the last menstrual period (LMP). The reason is that ovulation is rarely accurately determined without blood tests or ultrasound. A 28-day cycle ovulates around day 14, and from there it is approximately 266 days until delivery. By adding a full 280 days to the LMP, you arrive at the estimated due date. Individual variations occur, and an ultrasound scan in the first trimester can move the date up by a few days.
Pregnancy – body and mind in change
Pregnancy is a unique journey where both body and mind undergo significant changes – from the first hormonal fluctuations, which can cause fatigue and nausea, to the growing belly that reminds you of the little life inside. Many experience increased emotional vulnerability, but also a deep connection to the child and partner.
Give yourself time to rest, eat nutritious foods, and engage in light exercise such as walking or pregnancy yoga; this will improve circulation, mood, and sleep. Remember that every pregnancy is unique: listen to your body, and seek advice from your midwife or doctor if you are unsure about symptoms or need extra support.
Read more articles about pregnancy here .
Frequently asked questions
I don't know the date of my last period. What do I do?
Use the best estimate you have. Once you get your first scan, the date can be adjusted.
My cycle is longer/shorter than 28 days – does this affect my due date?
Yes. For example, if your cycle is 32 days, you will ovulate around day 18; adjust by adding the extra number of days before using the calculator.
The calculator shows a different due date than my scan. What applies?
Ultrasound in the first trimester is more accurate than the LMP method. Always follow the instructions of your midwife or doctor.
