Pregnancy due date calculator

What does 'due date' mean in pregnancy?
How is my expected due date (EDD) calculated?
What if I don't know my LMP or conception date?
How is my due date calculated if I had IVF?
How accurate are pregnancy due dates?

Have you tried adding, subtracting, multiplying and counting on your fingers to figure out your pregnancy due date? It can be confusing the work out the days, weeks and months. Use our handy pregnancy due date calculator to find out when your baby is due. All you need to do is enter the date of your last menstrual cycle and the calculator will do the rest!

What does due date mean in pregnancy?

Your due date is an estimated date when you're likely to give birth to your baby. It's also commonly referred to as EDD (expected due date).

Pregnancy lasts approximately 280 days. That’s nine calendar months and seven days, or 40 weeks. A pregnancy is considered full term at 37 weeks. The average pregnancy lasts between 37 weeks and 42 weeks.

How is my expected due date (EDD) calculated?

Very few expectant mums know exactly when they conceived. Unless you've been tracking your ovulation, there's no way to know for sure exactly when you ovulated and conceived. However, generally, most women ovulate about two weeks after the first day of their period, and conceive shortly afterwards.

Here are some ways to calculate your expected due date.

First day of your last period
The most common way to calculate your pregnancy due date is by counting 40 weeks or 280 days from the first day of your last menstrual period (LMP).

Add this length of time from the first day of your last period to get an idea of your due date. Our calculator uses this information to give you an estimated due date.

Conception date
If you do happen to know precisely when you conceived – say, if you were using an ovulation predictor kit or tracking your ovulation symptoms you can calculate your pregnancy due date based on your conception date.

Usually, women ovulate about two weeks after the first day of their period. So, count 38 weeks or 266 days from your conception date.

Keep in mind that you don't necessarily conceive on the day you had intercourse. Even if you only had sex once during your fertile period, you wouldn't conceive on that day unless you happen to be ovulating.

Sperm can live for up to five days inside your fallopian tubes. So, it could be up to five days after you had intercourse that you release an egg (ovulate) and it gets fertilised by a waiting sperm. That's the day you conceive.

What if I don't know my LMP or conception date?

If you don't know your LMP or conception date, speak to your doctor. She'll do a check-up and recommend you have an ultrasound scan. The scan will show how far along you are in pregnancy and determine your due date.

How is my due date calculated if I had IVF?

If you conceived through in vitro fertilization (IVF), you can calculate your due date using your IVF transfer date.

• If you had a Day 5 embryo transfer, count 261 days from your transfer date.
• If you had a Day 3 embryo transfer, count 263 days.

Your doctor will calculate your expected due date on the day of your embryo transfer. When you have your dating scan, your doctor will be able to give a more accurate EDD based on your baby's size and development.

How accurate are pregnancy due dates?

Your due date calculation is always approximate, whether it's from our tool or from your doctor.

No one can say for sure exactly when your baby will arrive. Only about four percent of babies are born on their due date!

Several factors can affect how your EDD is calculated. For example, if you don’t remember your LMP, or you have irregular periods or you don’t know when you conceived there will be a difference in the calculation.

To get a more accurate idea of when your baby is likely to be born, your doctor will perform a dating and viability scan, between six and nine weeks of pregnancy.

But even so, it is likely that your baby will arrive in the few weeks either side of your estimated due date. Knowing this can help you to be prepared for labour and birth, and to have everything ready for your new baby.


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• Pregnancy week by week
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• Sex during pregnancy