Pregnancy Due Date Calculator
Estimate your baby's due date, see how far along you are, and discover key pregnancy milestones.
Your Estimated Due Date
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The Ultimate Guide to Your Pregnancy Timeline
Congratulations on your pregnancy! This exciting journey is filled with anticipation and milestones, and one of the very first questions on every expectant parent's mind is, "When is the baby due?" Your estimated due date (EDD) is more than just a date on the calendar; it's the anchor for your entire pregnancy timeline, guiding prenatal care, developmental tracking, and preparations for your new arrival. Our Pregnancy Due Date Calculator is designed to give you a reliable estimate and a clear overview of the weeks and months ahead.
How to Use the Due Date Calculator
Our calculator offers two methods to estimate your due date, providing flexibility based on the information you have.
- Choose Your Calculation Method: Select either "Last Period" or "Conception Date".
- The Last Menstrual Period (LMP) method is the most common. It calculates the due date based on the first day of your last period.
- The Conception Date method is more accurate if you know the exact date of conception, for example, through ovulation tracking or fertility treatments like IVF.
- Enter the Date: Use the date picker to select the appropriate start date.
- View Your Results: The calculator will instantly display your estimated due date, your current gestational age (how many weeks pregnant you are), and the end dates for your first and second trimesters.
The Science Behind the Calculation
Naegele's Rule (LMP Method)
The standard method for calculating a due date from the LMP is known as Naegele's Rule. This simple formula assumes a regular 28-day menstrual cycle where ovulation occurs on day 14. The rule is:
Due Date = First Day of LMP - 3 Months + 7 Days + 1 Year
This is equivalent to adding 280 days (or 40 weeks) to the first day of your last period. It's important to note that the first two weeks of this "pregnancy" timeline are actually before conception has occurred. This is simply the standard medical convention for dating a pregnancy.
Conception Date Method
If you know the date you conceived, the calculation is more direct. A typical human pregnancy lasts about 38 weeks (266 days) from the date of conception. Our calculator adds 266 days to your provided conception date to estimate your due date.
How Accurate is a Due Date Calculator?
A due date calculator provides a very good estimate, especially if you have a regular menstrual cycle. However, it is just an estimate. Only about 5% of babies are born on their exact due date. Most babies arrive sometime between 38 and 42 weeks of pregnancy. The due date is best thought of as the center of a two-week window during which your baby is likely to be born.
For the most accurate dating, your doctor or midwife will likely perform an early ultrasound. By measuring the baby's size, they can determine a very precise gestational age and adjust your due date if necessary.
Your Pregnancy Timeline: The Three Trimesters
Your 40-week pregnancy is divided into three trimesters, each with unique developmental milestones for your baby and changes for you.
- First Trimester (Weeks 1-13): This is a period of rapid development. The baby's major organs and body systems are formed. You may experience symptoms like morning sickness, fatigue, and breast tenderness.
- Second Trimester (Weeks 14-27): Often called the "honeymoon" phase of pregnancy, as many early symptoms subside. You'll likely feel your baby move for the first time, and you may start to show more prominently.
- Third Trimester (Weeks 28-40+): The baby continues to grow and gain weight rapidly, preparing for birth. You will likely feel more tired and uncomfortable as your body prepares for labor and delivery.
Frequently Asked Questions (FAQ)
What if I have an irregular cycle?
If your menstrual cycles are consistently longer or shorter than 28 days, or if they are unpredictable, the LMP method will be less accurate. In this case, the date of conception method (if known) is a better choice. The most reliable method will be an early ultrasound performed by your healthcare provider.
What is gestational age?
Gestational age is the term used to describe how far along a pregnancy is. It is measured in weeks, from the first day of the woman's last menstrual period (LMP) to the current date. A normal pregnancy ranges from 38 to 42 weeks.
Can my due date change?
Yes, it's possible. Your initial due date is an estimate. Your healthcare provider may adjust it based on the results of your first ultrasound, especially if the ultrasound dating differs significantly from your LMP dating.