How to use the Due Date Calculator
For many parents, a positive pregnancy test result comes with a rush of excitement and joy. Once you’ve processed the news, thoughts will naturally turn to planning your little one’s arrival. One of your first questions will no doubt be: when is my due date?
With the help of the Due Date Calculator, these three simple steps will help you determine how far along you are in your pregnancy:
- Figure out when was the first day of your last period or the exact day you conceived.
- Enter the relevant dates into the Due Date Calculator.
- Then hit “Calculate your due date!”for your results. It’s that simple!
Keep in mind every pregnancy is unique and the result will be an estimation rather than a fixed date.
What is an estimated due date, and can it change?
A due date, or estimated due date, is a prediction of when you will give birth. It will help you to track the various stages of your pregnancy, which milestones to expect and when.
Which calculation method should I choose?
Your due date can be estimated in several ways: the date of your last period, conception date, IVF-transfer date, or using an early ultrasound. With our Pregnancy Due Date Calculator, we based our estimations on either the date of your last period or your conception date.
The first day of your last period: While it’s true that most pregnancies last 40 weeks, there are other factors at play which will determine your due date. Most expectant mothers don’t realize that both menstrual and ovulation periods count as the first two weeks of pregnancy.
Many won’t be aware of their pregnancy until their first missed period, and by that time they could be up to five weeks in. That means that simply estimating nine months from the day you take a pregnancy test isn’t going to calculate your due date, and, even so, factoring in a few weeks here and there for ovulation won’t either.
Unless you can pinpoint exactly what point of your ovulation cycle you were in at the time of fertilization, it’s difficult to know how far along you are and what date you’ll meet your baby. Luckily, our Due Date Calculator can help.
This method of predicting your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period - a common method used by a healthcare provider to estimate your due date if you have not yet had an ultrasound.
If you choose this calculation method, our Due Date Calculator will quickly work out your estimated due date, using both the date of your last period and the length of your regular cycle (tailoring it accordingly for longer, shorter, and average cycle lengths).
Conception date: If you know exactly when your baby was conceived, you can use this date to make a prediction of how far along you are. In the same process as the last menstrual period method, 266 days are counted from the conception date to get an estimated due date.
With our Pregnancy Due Date Calculator, input your preferred method and dates, then the calculations are made for you. Remember, your due date is only an estimate. Every baby is unique, and your little one might arrive outside of this timeframe.
What about with IVF?
In the case of in-vitro fertilization (IVF), it’s possible to calculate an estimated due date using the IVF transfer date – that’s the date that the fertilized eggs are implanted in the uterine wall. The transfer time will vary between individuals. Speak to your healthcare provider for more information about this calculation method.
Can my due date change?
Yes! Even with careful planning to predict your due date, only around 1 in 20 women give birth on their due dates. Although your healthcare provider will do their best to accurately estimate your due date, there are a few reasons why it might change as your pregnancy progresses. For example, if you use the last menstrual period method, it might be that an irregular period impacts the accuracy of the calculation. Or maybe the date of your first ultrasound actually happens in the second trimester.
Now that I have my estimated due date, what next?
Once you’ve calculated your due date, you can get a better idea of when to expect your little one and start to plan accordingly.
If you haven’t done so already, one of the first steps to take is to schedule an appointment with your doctor, who can confirm that you're pregnant via a blood test and physical exam.
To help you establish a more precise due date at your first prenatal care appointment, your healthcare provider will determine the size of your uterus and monitor fetal growth. Pregnancy milestones such as hearing your baby’s first heartbeat and seeing your baby via ultrasound will be a thrilling part of these checkups. Along the way, depending on what is observed, your pregnancy due date may be adjusted.
While your doctor will be able to advise you best, there are still plenty of things you can do as soon as you discover you’re pregnant. Why not follow your milestones via your mobile calendar with the Pregnancy Milestones Tracker tool?
How we wrote this page:
The information in this page is based on the expert advice found in medical and government sources, such as the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists. You can find a full list of sources for this tool below. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.