Childbirth

Due Date Calculator: Find Out Your Baby’s Due Date

Wondering when your due date is? Use our nifty due date calculators to learn exactly when to expect your little one and know just how far along you are in your pregnancy.

When you first find out you are pregnant, you may have a lot of questions going through your mind. However, if you have decided to carry your pregnancy to term, there is probably one big question you have: When is my due date?

If you’re wondering how to calculate due date for your pregnancy, you’re in luck. There are many due date calculator websites out there to help you determine when your little one will arrive, and this webpage is one of them. At UnplannedPregnancy.com, we know how important it is to plan for your little bundle of joy — and knowing exactly when to expect them is always the first step!

Below, you’ll find all the helpful information you need to learn about pregnancy due dates and how to determine the due date of your pregnancy. However, remember: The information in this article is not intended to be taken as medical advice and should not replace a due date estimate provided by your personal obstetrician. If you haven’t yet, schedule your prenatal appointments as soon as possible to receive the most accurate estimate for your pregnancy.

First: The Biggest Misconception About Pregnancy Due Date

If you know anything about pregnancy, you know that due dates are calculated based on a 40-week pregnancy calculator. If you’re like most people, you may think that those 40 weeks are from the day your baby is conceived — but that’s actually not true.

When it comes to estimating an expected due date, doctors and other medical professionals need to know an important detail: the first day of your last period. This is because the 40 weeks of a typical pregnancy actually include your menstrual period and ovulation. The first two weeks of your pregnancy are not the first two weeks after conception; they are the two weeks prior to conception. When your baby is born, he or she is actually 38 weeks old — not 40 weeks.

So, before you go asking, “What is my due date?” you should identify what the first day of your last period was. Only by knowing this can you receive the most accurate estimated due date for your pregnancy.

How to Calculate Due Date

As mentioned above, before you start using any pregnancy due date calculator, it’s important that you know the first day of your last period. If you are using a period tracker, this can be easy to remember. If not, you will need to think back to this time in order to best aid your doctor and any due date predictor you may utilize.

One more thing to know before you get started: A baby due date is simply an estimate and a target date. Many women deliver a week or two before or after their due dates; in fact, only 5 percent of births take place exactly on the estimated due date. This is why it’s so important to keep your doctor up to date on your pregnancy — to ensure your baby is developing normally and delivering slightly early or delayed won’t harm either of you.

Remember, your doctor is always the best “baby due date calculator” there is but, in the meantime, here are a few ways you can estimate your personal due date:

Due Date by First Day of Last Menstrual Period

If you wanting to know how to calculate your due date, counting from the first day of your last period is often the most accurate (and easiest) way to do so. You will want to count 40 weeks (280 days) from the first day of your last period to estimate when your little one will arrive. For example, if your last period started on January 2, your due date will be 40 weeks from then — October 29. You can also subtract three months from the first day of your last period and add seven days.

Either of these methods will give you a good estimate of your pregnancy due date.

Due Date By Conception Date

While using the date of your last period is often the best way to calculate your due date, sometimes women ask, “What is my due date based on conception date?” If you have a good guess of when your conception date is (for example, you only had sex once or twice during your last menstrual cycle, or you used an in vitro fertilization transfer), you can use that date to estimate your baby’s arrival. Simply add 38 weeks (266 days) to get your estimated due date.

Keep in mind: Sperm can live inside a woman’s body for up to five days, and an egg can live for up to 24 hours after being released. For this reason, it can be difficult to pinpoint an exact conception date. Instead, you may wish to calculate based on your ovulation, the six-day window in which you can potentially get pregnant.

Due Date Based on Ovulation

Other expectant mothers want to calculate their due date by ovulation. This is simple: Because your ovulation typically occurs a week after your menstrual period, you can calculate your due date by adding 39 weeks (273 days) to your ovulation date. Remember, this is because your menstrual period is counted as your first week of pregnancy.

In other cases, women want to know due date based on ovulation so they can plan to give birth at a certain time during the year. While this can be a good idea, it is difficult to “control” your due date and pregnancy in this way. Even if you conceive at a given time, there is still a bit of unpredictability when it comes to the day, week and even month that you actually deliver!

Something else to keep in mind: Due date calculators work based on the assumption that a woman’s monthly cycle last 28 days, with ovulation occurring on day 14. This may not be the case for everyone, so calculating by your conception or ovulation date is usually not 100 percent accurate.

How Far Along Am I By Due Date?

So, you’ve found out your due date — congrats! You can start counting down the days until you meet your little one.

But, you may have another question at this point: How many weeks pregnant am I by my due date?

Like many expectant mothers, you may be curious about what you can expect at each week in your pregnancy. Your body will change a lot during the next 40 weeks, as will your developing baby. Knowing where you are in your pregnancy can help you anticipate these changes and do what is best for your health and your baby’s health.

So, if you know your due date and want to know how many weeks you are, simply count back from your due date to today’s date. However many weeks there are between your due date and the current date, take that number and subtract it from 40. That will tell you how many weeks you are by your due date!

Once you have determined where you are in your pregnancy, you can find out exactly what to expect from each trimester of pregnancy here:

However, your doctor is always the best person to guide you through the different weeks of pregnancy — just as they are the best “pregnancy due date calculator” out there. Haven’t found a doctor yet? Start your search today to begin your pregnancy on the right foot.