Due Date Calculator
Congratulations! You’re about to embark on one of life’s most incredible journeys—becoming a mom. As soon as you suspect you’re pregnant, one big question pops into your mind: When is my baby due?
A pregnancy due date calculator offers a good estimate, though it’s important to remember that it's just an approximation. Only about 4% of babies are actually born on their estimated due date, with most arriving between 37 and 42 weeks.
Using our Pregnancy Due Date Calculator, you can estimate your due date based on your last menstrual period, conception date, IVF transfer, or ultrasound. Here's how these methods work and what factors can influence the timing of your baby’s birth.
What Is a Pregnancy Due Date?
Your due date is when your baby ought to be born – approximately 40 weeks since the beginning of your last period (LMP). Most babies do not actually arrive on this exact date, so doctors just call it an "estimated" due date.
This date is convenient to use when tracking pregnancy milestones and scheduling your prenatal care, testing, and ultrasound. This also helps get you ready mentally for when your baby is going to be born!
How Is Your Due Date Calculated?
Doctors use several reliable methods to figure out when your baby will arrive. Here are the main ways your due date might be determined:
Using Your Last Period (Naegele's Rule)
The most common method starts with the first day of your last period. Your doctor will add 40 weeks (280 days) to this date.
There's a handy shortcut:
Due Date = First Day of LMP + 1 year - 3 months + 7 days
For instance:
If your last period began May 1, 2025:
Due Date = May 1, 2025 + 1 year - 3 months + 7 days = February 8, 2026
This works best if your cycles are consistently 28 days. If they're shorter or longer, the estimate might be a bit off.
Counting From Conception
If you know approximately when you got pregnant, then you can have a better estimate. Just put 38 weeks (266 days) on top of your date of conception.
For example:
If you conceived on June 1, 2025:
Due Date = June 1, 2025 + 266 days = February 22, 2026
This method is especially helpful if you've been tracking ovulation or had fertility treatments.
Ultrasound Dating
An early ultrasound is another way to estimate your due date. During the first trimester (usually between 8–14 weeks), your healthcare provider will measure your baby’s crown-to-rump length (CRL). This measurement helps determine the gestational age and gives a more accurate due date, especially if you’re unsure about your LMP.
This method is particularly valuable if you have irregular periods or can't remember when your last period started.
IVF Due Date Calculation
If you conceived through in vitro fertilization (IVF), your due date is calculated based on the embryo transfer date. This method is very precise:
- For Day 3 transfers: Add 263 days to your transfer date
- For Day 5 transfers: Add 261 days to your transfer date
For example, if your embryo transfer was July 1, 2025: - Day 3 Transfer: Due Date=July 1, 2025+263 days=March 20, 2026
- Day 5 Transfer: Due Date=July 1, 2025+261 days=March 18, 2026
Why Knowing Your Due Date Matters
Once you know your due date, you can start planning. It’s like knowing the end of a marathon—you understand when you’ll cross the finish line, but the journey is what you need to focus on. Here’s why knowing your estimated due date is important:
Tracking Pregnancy Milestones
Knowing your due date helps you track your baby’s development and your pregnancy milestones. For example, by week 12, many women start to feel relief from morning sickness, and by week 20, you might start feeling your baby’s first kicks.
Preparing for Labor and Delivery
Your due date gives you time to plan for the big day. You can pack your hospital bag, arrange for maternity leave, and prepare your home for your baby.
It also allows you to think about your birth plan, whether you want a natural birth or an epidural. The estimated due date helps you feel ready and organized.
Scheduling Medical Appointments
Key prenatal appointments, like your first ultrasound and screenings for gestational diabetes, are based on your due date. Your healthcare provider uses your pregnancy due date to schedule these tests at the right time in your pregnancy.
Can Your Due Date Change?
Yes, your due date can change. Several factors, such as irregular menstrual cycles, late ovulation, or early ultrasound measurements, can cause your doctor to adjust your due date.
Pregnant women carrying twins or experiencing certain medical conditions may also see their due dates change. While you can try to predict or influence your due date, the truth is that babies arrive on their own schedule.
How Accurate Is Due Date Prediction?
Even with all the science and tracking, predicting your baby’s exact arrival day is tricky. Only about 4% of women give birth on their due date.
Most babies arrive somewhere between 37 and 42 weeks, and about 80% of them are born within 10 days of their due date.Babies can arrive early or late, and both are usually perfectly normal.
Factors That Can Influence or Change Your Due Date
While your due date offers a decent window for preparing for your baby's arrival, there are several factors that can shift this estimate along the way.
Variations in Menstrual Cycles
If your periods are irregular, predicting your due date can be more challenging. Women with irregular cycles might ovulate earlier or later than the typical 14-day window, making it harder to pinpoint when conception happened.
Early Ultrasound Adjustments
As mentioned earlier, your doctor may adjust your due date if your ultrasound shows that your baby’s size doesn’t match up with the date calculated from your LMP.
This is especially common if you have irregular periods or if you conceived while on birth control, which can make your cycle unpredictable.
Twin or Multiple Pregnancies
If you’re carrying more than one baby, your due date might be a little different. Twin pregnancies often result in earlier deliveries, so you might not make it to your full 40 weeks. In fact, many twin pregnancies deliver between 36 and 38 weeks.
Medical Conditions That Can Alter Your Due Date
Certain health conditions, like gestational diabetes or high blood pressure, might cause your doctor to recommend inducing labor before your due date.
In these cases, your “due date” might change based on your health and how well your pregnancy is progressing.
How Soon Can You Take a Pregnancy Test?
If you're eager to know if you're pregnant or not, timing is of the essence when it comes to a pregnancy test. The test can even show a false negative result even if you're pregnant if taken too early.
When Is the Best Time to Take a Pregnancy Test?
The best time to take a pregnancy test is about a week after your missed period. By that point, your body should have produced enough human chorionic gonadotropin (hCG) to show up on a test.
Some tests claim to detect pregnancy earlier, but for the most accurate results, it’s best to wait.
What if My Pregnancy Test Is Negative?
If your test comes back negative but you still think you might be pregnant, wait a few more days and try again. Sometimes hCG levels aren’t high enough in the early days to be detected.
If your period still hasn’t arrived, contact your healthcare provider for a blood test, which is more sensitive to low levels of hCG.
If you’re not pregnant, using an ovulation calculator can help you better predict when you’re most likely to conceive. Ovulation typically occurs about 14 days before your next period, which is your most fertile time.
What to Do After a Positive Pregnancy Test
Once you’ve confirmed you’re pregnant, it’s time to take action. You’ll want to get into the best shape possible for your baby and yourself. Here’s what you should do next:
Book Your First Prenatal Appointment
Your first prenatal visit usually happens around 8-10 weeks of pregnancy. At this appointment, your doctor will confirm your pregnancy, estimate your due date, and check your overall health.
They’ll also give you a roadmap for the months ahead, including what tests and ultrasounds you’ll need and when.
Start Tracking Your Baby’s Development
Every week brings new developments for your growing baby. At eight weeks, your baby is about the size of a raspberry, and by week 20, they’re the size of a banana. It’s exciting to track these milestones and see how much your little one changes.
Lifestyle Changes for a Healthy Pregnancy
Now is the time to make sure you’re eating well, staying active, and taking prenatal vitamins. You’ll want to avoid alcohol, tobacco, and certain foods that can harm your baby, like raw fish and unpasteurized cheese.
Staying healthy during pregnancy helps ensure your baby is getting the best possible start.
For fun, you might also try using a Chinese gender predictor to playfully guess your baby’s gender.
Frequently Asked Questions
What is the most accurate way to calculate pregnancy due date?
The most accurate way to calculate your due date is by using the first day of your last menstrual period (LMP). Generally, doctors add 280 days (or 40 weeks) to this date to estimate your due date.
However, an early ultrasound, usually done in the first trimester, can provide more accuracy, especially if you're unsure about your LMP.
Which due date is correct in pregnancy?
The due date estimated by your healthcare provider, usually based on your LMP or early ultrasound, is the most reliable. However, it's important to remember that this is just an estimate.
Only a small percentage of women give birth on their exact due date, as it's more of a general guide than a set date.
Which due date is most accurate?
The due date from an early ultrasound (typically done between 8-13 weeks of pregnancy) is generally considered the most accurate. It’s especially useful if you’re unsure of your LMP or have irregular cycles.
What week am I actually pregnant?
Your pregnancy is typically dated from the first day of your last menstrual period. So, when you find out you're pregnant, you may already be about 4-6 weeks along, depending on when you took the test and the timing of your last period. An ultrasound can help clarify how far along you are.
Can ultrasound detect the exact date of pregnancy?
An early ultrasound can give a very accurate estimate of how far along you are, but it cannot pinpoint the exact date of conception. It can estimate your due date based on the size and development of the fetus, which is most accurate in the first trimester.
Pregnancy Week by Week
