Due Date Calculator
Positive test? Congratulations! The very next question: when is baby arriving? Our calculator gives you your estimated due date (EDD), your pregnancy stage in weeks of amenorrhea (WA), the recommended windows for your three ultrasounds, and the key dates for your paperwork, all in a few seconds.
Where are you at?
Your 3 ultrasounds
Your key dates
This tool provides an estimate for guidance only. Only a healthcare professional, particularly during the dating ultrasound, can confirm your due date.
How is the due date calculated?
A pregnancy lasts an average of 280 days, or 40 weeks of amenorrhea, counted from the first day of your last period. This is the famous Naegele's rule, used by midwives and gynecologists around the world: you start from the date of your last period, add 14 days to estimate ovulation, then 9 months.
Our calculator refines this calculation using the length of your cycle. If your cycles last 33 days instead of 28, you ovulate about 5 days later, and your due date shifts by the same amount. That is why we ask for the average length of your cycle: a detail that many calculators ignore.
If you know your exact conception date (temperature chart, ovulation test, IVF), use the second calculation mode: pregnancy then lasts an average of 266 days from fertilization.
Weeks of amenorrhea (WA) or weeks of pregnancy: don't mix them up anymore
This is the most common confusion in early pregnancy. Weeks of amenorrhea (WA) are counted from the first day of your last period. Weeks of pregnancy (WP) are counted from conception, about two weeks later. So you always have: WA = WP + 2.
Your medical follow-up, your prescriptions and your ultrasounds almost always use WA. When your gynecologist says "you are at 12 WA," you have been pregnant for about 10 weeks. Our calculator gives you both, so you never have to wonder again.
Irregular cycle, IVF: which calculation is right for you?
With irregular cycles, the ovulation date becomes hard to predict and the calculation based on your period is less reliable. In this case, enter the average length of your last three cycles, and keep in mind that the first-trimester dating ultrasound will adjust your due date with an accuracy of 3 to 5 days.
For an IVF pregnancy, on the other hand, the calculation is the most precise there is: the fertilization date is known to the day. Use the "conception date" mode with the date of the egg retrieval or the transfer (subtracting the age of the embryo at transfer: for a 3-day-old embryo, count conception as 3 days before the transfer).
An estimate, not a promise
Let's be honest: fewer than 5% of babies are born on their exact due date. The vast majority of births happen within a window of two weeks before or after. A birth between 37 and 42 WA is considered full term.
The date that counts medically is the one set during the first-trimester ultrasound, known as the dating ultrasound, performed between 11 and 13 WA: measuring the embryo's crown-rump length makes it possible to date the start of the pregnancy to within a few days, even if you no longer remember your last period.
Want to add a little tradition to the science? Have fun with the Chinese pregnancy calendar or the Mayan calendar to guess whether you are expecting a girl or a boy.
You have your date: the next steps
Now that you have your EDD, here is your roadmap:
- Before the end of the 14th WA: declare your pregnancy. Your doctor or midwife sends the declaration to your health insurance fund and to the CAF (the French family allowance fund) at the first prenatal exam, usually at the time of the dating ultrasound. This declaration opens up your rights (100% coverage from the 6th month, birth allowance subject to income conditions).
- Between 11 and 13 WA: dating ultrasound, which confirms or adjusts your due date.
- Between 22 and 24 WA: anatomy ultrasound, the most thorough one, often the one where you find out the baby's sex. This is the moment many parents choose to plan their announcement or gender reveal.
- Between 32 and 34 WA: third-trimester ultrasound, which checks the baby's growth and position.
- 6 weeks before the EDD: start of the statutory maternity leave for a first or second child (16 weeks in total: 6 before, 10 after).
And at the very end of pregnancy, when every day counts, discover the signs that labor is near and the old wives' tips to help you wait.
Get the nest ready while you wait for baby: between the declaration and the ultrasounds, the second trimester is the ideal time to set up the nursery. Get inspired by our bed canopies and baby night lights to create a cozy cocoon.
Frequently asked questions
Is the due date calculation reliable?
The calculation based on your last period gives a reliable estimate to within a week for regular cycles. The reference remains the dating ultrasound between 11 and 13 WA, accurate to within 3 to 5 days. Use our calculator to plan ahead, and let your healthcare professional confirm the official due date.
I don't remember the date of my last period. What should I do?
Don't panic. If you know roughly when you conceived, use the second calculation mode. Otherwise, the dating ultrasound will determine your due date without needing any date at all: that is exactly its purpose.
My cycles are irregular. Is the result valid?
With irregular cycles, enter the average length of your last three cycles to refine the estimate. The result remains indicative: the first-trimester ultrasound will adjust the date precisely.
I'm expecting twins. Does my due date change?
The calculation of the theoretical due date stays the same, but twin pregnancies often end earlier: half of all twins are born before 37 WA. Your medical team will adapt your follow-up and will probably anticipate the actual date of birth.
What happens if I go past my due date?
This is common, especially with a first baby. In France, closer monitoring begins on the due date itself, and induction is generally offered between 41 and 42 WA if labor does not start naturally.
How do I convert weeks of amenorrhea into months of pregnancy?
Keep a few benchmarks in mind: 1 month = 6 WA, 3 months = 15 WA, 6 months = 28 WA, 9 months = 41 WA. Our calculator directly shows your stage in WA, in weeks of pregnancy, and the current trimester.
The information on this page is provided for informational purposes only and does not replace medical advice. Consult your doctor, gynecologist or midwife for any question about your pregnancy.