3 Ways to Calculate Your Baby’s Due Date

There is nothing as exciting as finding out that you are pregnant and about to add a new life to your own life. If only you knew the precise due date, which you can but it is always just estimations. In fact, only about 5% of births happen on their expected due date.

Pregnancies usually differ, meaning some babies come before or after their estimated due date. Nevertheless, you can easily figure out your estimated due date if you are well aware of the first day of your last recent period.

You should also stay in touch with a doctor to ensure everything is moving on, as expected. Besides, a doctor can help you determine the most precise estimation of your birth date.

There are three common ways in which, you can calculate your baby’s due date. You can use an online due date calculator, or count the weeks manually. You can also get an ultrasound.

Here is a look at these three methods in detail.


  • Use an Online Due Date Calculator


If you want to calculate your estimated due date using an online calculator, choose one that appeals to you. As there are many types, that choosing one might be hard. You can opt for those in reputable maternity websites or ask for recommendations from your clinic or fellow mothers.

After which, you can enter the first day of your last recent period or day of conception, depending on what the online due date calculator is asking. However, date of conception can be hard to know, unless you have had IVF treatments or use ovulation tracker.

As much as the online calculator will give you an estimation of your due date, always consult a doctor for confirmation and clarification on when exactly your bundle of joy is due for arrival. However, note that it is still just estimations, the baby can come in early or later, but at least you will be prepared.


  • Count the Weeks Manually


Here you will have to determine the first day of your last period before you found out you were pregnant. The first day of your last period represents the first day of your cycle, and conception usually occurs 11-21 days after the first day of the last period.

Note that sperm can survive for a few days after intercourse, thereby being in a position to fertilize any released egg.

You can then count 40 weeks or 280 days from the first date of your last recent period, to determine your due date. Even though pregnancies usually last for 37-38 weeks, the 40-week estimation is drawn because conception occurs 2-weeks after the first date of your last menstruation.

Alternatively, you can calculate your due date by using Naegele′s rule, of counting three months back from the first day of your recent last period, before getting pregnant. Add seven days to the date you find three months back, and then add a year and you have your estimated due date.

Likewise, you can add 9 months 7 days to the first day of your last recent menstrual period, to get your estimated due date.

However, you should take note that using the first day of your last period with this rule, only works best if you have a 28-day cycle. Therefore, if you have irregular periods, it is better to see a doctor who can perform an ultrasound to determine your estimated due date.


  • Use an Ultrasound


An ultrasound is the most accurate way to estimate your due date, but only if you do it in between week 8-18+ in your pregnancy, not less. It is way better and accurate than calculating your due date by the first day of your last menstruation.

However, if the doctor has the date of the first day of your last period while performing the ultrasound, he/she can easily pinpoint when the baby will arrive accurately.

An ultrasound will be done on your stomach to see the progress of the baby but in case of any issue or for a better view. The doctor might recommend a transvaginal ultrasound. Overall, you can easily get to know when you are due for delivery.


In conclusion, you still need to see a doctor no matter how accurate you think you are due to deliver your baby. A doctor will help you monitor the baby’s development, as the months go by.

Nonetheless, above are three best ways to calculate your baby’s due date. You can opt for the most convenient one or all.