Pregnancy calculator: Everything you need to know about your due date and pregnancy week

Expecting? Curious about your due date? The pregnancy calculator helps you estimate your due date, track your baby's development, and stay on top of recommended checkups.

 A pregnant woman holding an ultrasound image (photo credit: SHUTTERSTOCK)
A pregnant woman holding an ultrasound image
(photo credit: SHUTTERSTOCK)

If you've made it this far, it means you deserve a big "mazel tov!" Like all expecting parents, especially if this is your first pregnancy, you're probably eager to know everything that's happening and what lies ahead in the next nine months.

One of the first questions you'll ask yourself is: "Which week of pregnancy am I in?" While a pregnancy calculator helps with that, it’s just the beginning. The calculator also assists in tracking your baby’s growth and the changes in your body during pregnancy. It gives you insights into each stage and helps you stay informed about the recommended medical tests as you embark on this remarkable journey.

Let’s clarify things by explaining what a pregnancy calculator is, how it divides pregnancy into weeks, months, and trimesters, and the changes you and your baby will experience along the way. We'll also cover the advanced tests you'll need to consider during this time.

What Is a Pregnancy Calculator?

Pregnancy typically lasts around 40-42 weeks from the first day of your last menstrual period, divided into three trimesters. Each trimester represents a distinct stage in pregnancy, each with its own symptoms and medical tests.

The good news is that from now on, you won’t have to worry about dates and calculations. A pregnancy calculator does all that for you, and it's easy to use.

The pregnancy calculator uses the date of your last period to predict your due date. It’s based on an average pregnancy of 40 weeks. So, to calculate the current week of pregnancy, the calculator counts 280 days (40 weeks) from the first day of your last menstrual period. With this tool, you can access detailed information about each week and trimester of your pregnancy, learn what’s happening with your body, and discover the recommended tests for each stage.

 A pregnant woman (credit: INGIMAGE)Enlrage image
A pregnant woman (credit: INGIMAGE)

While the pregnancy calculator is highly useful, it’s important to note that slight inaccuracies can occur due to individual differences in fetal development, which can vary from baby to baby. Nevertheless, it's still an excellent tool for expecting mothers.

How Do I Calculate Which Week I'm In and My Due Date?

You’ve taken a home pregnancy test, and it came back positive—how exciting! But maybe you haven’t visited your gynecologist for an official diagnosis yet. That’s where the pregnancy calculator comes in handy. After entering the first day of your last period, or your conception date if you know it, the pregnancy calculator will estimate your current pregnancy week and provide an approximate due date. You’ll also receive updated information for that week, including details on the baby’s development, bodily changes, and recommended tests. However, it's always advisable to visit your doctor to confirm the pregnancy and ensure everything is progressing well.

Why Is It Important to Know Which Week You're In?

Knowing your due date is not only important for you but also for the medical team guiding you through your pregnancy. Tracking pregnancy weeks is essential for both the mother’s and the baby’s health. Beyond the excitement and changes in family dynamics, this tracking is critical for planning the birth, scheduling tests at the appropriate times, and monitoring the baby’s development.

With You Every Step of the Way

Your baby’s development is a fascinating journey, where each week brings new growth and formation of vital organs, leading to a fully developed baby ready to enter the world. The pregnancy calculator helps you feel more connected to your baby, better understand the changes happening to both of you, and manage the adjustments to your body.


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The pregnancy calculator provides clarity and reassurance during this exciting period. It helps you know where you are in your pregnancy, what to expect during each week for both your baby and yourself, guides you on the necessary medical tests, and ensures a healthy and successful pregnancy.

By Dr. Jacob Segal, in collaboration with Maccabi Healthcare Services