Pregnancy Due Date Calculator

Our pregnancy due date calculator will not only reveal your possible due date but also provide important milestone notes, explain when a doctor may perform specific routine tests during pregnancy, and even give you a rough estimate of your baby’s size.

Our calculator also includes links to week-specific articles for every week left in your pregnancy. Our week-by-week pregnancy guides share information about baby’s development, milestones for expecting mothers, doctor’s visits, and other information about what expecting moms still have to look forward to before their little bundle of joy arrives.

Important note: Below this calculator are the various ways you can calculate your due date using a pregnancy due date calculator. If you’re unsure which method to use, read the information below and return to the calculator. Once you enter your data, the calculator will populate with helpful information to guide you during your pregnancy journey.

One of the first questions expecting parents ask is, “When is my baby due?” While an exact birth date can’t be predicted, doctors use several reliable methods to estimate the due date.

he most commonly used calculation is based on the last menstrual period, but factors like conception date, in vitro fertilization (IVF), and ultrasound findings can also provide accurate estimates.

Here’s a breakdown of the five main ways to calculate your pregnancy due date, all available in the drop-down menu for our pregnancy due date calculator featured at the top of this post.

Pregnancy Due Date: Using the Last Menstrual Period (LMP)

The most common method for estimating a due date is by using the first day of the last menstrual period (LMP). This method is based on Naegele’s Rule, which assumes a 28-day menstrual cycle with ovulation occurring on day 14. The formula adds 280 days (40 weeks) to the first day of the LMP to predict the estimated due date (EDD).

Example Calculation:

• If your last period started on March 1, adding 280 days (or subtracting three months and adding seven days) would result in an estimated due date of December 6.

This method is most accurate for those with regular menstrual cycles. However, if you have irregular cycles or ovulate earlier or later than average, your actual due date may vary.

Pregnancy Due Date: Using the Conception Date

If you know the exact date of conception—whether from tracking ovulation or undergoing assisted reproductive technology—you can calculate the due date by adding 266 days (38 weeks) from conception. This method accounts for the fact that pregnancy technically begins at conception rather than at the start of the last menstrual cycle.

Example Calculation:

• If conception occurred on April 15, adding 266 days would give an estimated due date of January 6.

This method works best for individuals who closely track ovulation or those who conceived through fertility treatments.

Pregnancy Due Date: IVF Due Date Calculation for a 3-Day Embryo Transfer

For pregnancies achieved through in vitro fertilization (IVF), the due date is calculated based on the embryo transfer date. If a 3-day embryo was transferred, conception is considered to have occurred three days before the transfer. From that date, a standard 266-day pregnancy length is applied to estimate the due date.

Example Calculation:

• If a 3-day embryo transfer was performed on May 10, conception is estimated to have occurred on May 7. Adding 266 days gives an estimated due date of January 28.

Pregnancy Due Date: IVF Due Date Calculation for a 5-Day Embryo Transfer

A 5-day embryo transfer assumes conception occurred five days before the transfer. The calculation is the same as with a 3-day transfer, except it adjusts for the embryo’s developmental stage at implantation.

Example Calculation:

• If a 5-day embryo transfer was performed on June 5, conception is estimated to have occurred on May 31. Adding 266 days gives an estimated due date of February 21.

This method is highly accurate because the exact timing of conception is known, eliminating uncertainties associated with natural conception.

Pregnancy Due Date: Ultrasound-Based Due Date Calculation

If you’re unsure of your last menstrual period or have irregular cycles, an ultrasound can provide a reliable due date estimate. During an early ultrasound (typically between 6 and 12 weeks), a healthcare provider will measure the baby’s crown-rump length (CRL) to determine gestational age. The due date is then calculated based on how far along the pregnancy is at the time of the ultrasound.

Example Calculation:

• If an ultrasound performed on August 1 measures the baby at 8 weeks, 3 days gestational age, the conception date would be estimated as June 6, and the due date would be March 14.

Ultrasound dating is most accurate in the first trimester. As pregnancy progresses, fetal size can vary more significantly, making later ultrasounds less reliable for dating.

Choosing the Most Accurate Method For Your Pregnancy Due Date

• If you have a regular cycle, using the LMP method is a straightforward and widely accepted approach.
• If you track ovulation or know the exact conception date, that method will be more precise.
• If you conceived via IVF, using the embryo transfer date is the best way to calculate your due date.
• If you’re unsure about dates or have irregular cycles, an early ultrasound provides the most accurate estimate.

Regardless of the method used, only about 5% of babies are born on their exact due date, so it’s best to view this estimate as a guideline rather than a guarantee. Your healthcare provider will monitor your baby’s growth and development to ensure the most accurate tracking throughout pregnancy.