🤰🏻 Pregnancy Due Date Calculator

Calculate your estimated due date (EDD), current pregnancy week and trimester using your last menstrual period (LMP).

A Pregnancy Due Date Calculator helps you estimate your baby’s expected delivery date based on the first day of your last menstrual period (LMP). It can also help you understand your current pregnancy week, trimester, and estimated time remaining until delivery.

Use the calculator above by entering the first day of your last menstrual period.

The calculator will then estimate your expected due date and pregnancy timeline.

How Does the Pregnancy Due Date Calculator Work?

A typical pregnancy is estimated to last around 40 weeks, or 280 days, from the first day of the last menstrual period.

The calculator uses your LMP date as the starting point and estimates the expected delivery date by adding 280 days.

For example, if the first day of your last menstrual period was January 1, the estimated due date would be around October 8.

This is an estimate rather than an exact prediction. The actual date of delivery can occur before or after the calculated due date.

How to Use the Pregnancy Due Date Calculator

Using the calculator is simple:

1. Enter the first day of your last menstrual period.
2. Check the calculated estimated due date.
3. Review your estimated pregnancy week.
4. Check your current trimester.
5. Use the result to understand your approximate pregnancy timeline.

For the most useful result, make sure the LMP date you enter is as accurate as possible.

What Is a Pregnancy Due Date?

Your estimated due date (EDD) is the approximate date when your baby is expected to be born.

It is important to understand that the due date is not a fixed delivery date. Only a small proportion of babies are born exactly on their estimated due date.

The calculated date is mainly used as a reference point for monitoring pregnancy progress and planning antenatal care.

How Is the Estimated Due Date Calculated?

The traditional calculation is based on Naegele’s rule.

Estimated Due Date = First Day of LMP + 280 Days

This calculation assumes an average menstrual cycle of approximately 28 days with ovulation occurring around the middle of the cycle.

Because menstrual cycles can vary, the calculated date may not perfectly represent the actual gestational age.

What If My Menstrual Cycle Is Longer or Shorter Than 28 Days?

A standard due date calculation generally assumes a 28-day menstrual cycle.

If your cycle is consistently longer or shorter, ovulation may occur at a different time. This can affect the estimated due date.

For this reason, your healthcare professional may adjust the estimated date based on your menstrual history and, when appropriate, ultrasound findings.

How Many Weeks Pregnant Am I?

Pregnancy is commonly measured in weeks rather than months.

Gestational age is calculated from the first day of your last menstrual period, not from the day of conception.

For example:

• 1–13 weeks: First trimester
• 14–27 weeks: Second trimester
• 28 weeks onward: Third trimester

Your exact pregnancy week depends on the date entered into the calculator and the current date.

Pregnancy Due Date vs Conception Date

The pregnancy due date is not calculated by simply adding nine months to the date of conception.

Medical pregnancy dating usually starts from the first day of the last menstrual period. Because ovulation and conception generally happen later, pregnancy is counted as approximately 40 weeks from LMP even though conception usually occurs about two weeks after the start of that menstrual cycle.

This is why the gestational age can appear to be about two weeks ahead of the time since conception.

How Accurate Is a Pregnancy Due Date Calculator?

A due date calculator provides an estimate, not a guaranteed delivery date.

The accuracy depends on several factors, including:

• How accurately the LMP date is known
• Menstrual cycle length and regularity
• Timing of ovulation
• Whether the pregnancy followed a typical menstrual pattern
• Ultrasound-based dating when clinically indicated

If you are unsure about your LMP or have irregular periods, your healthcare professional may use other information to establish or adjust pregnancy dating.

Can an Ultrasound Change My Due Date?

Yes. An ultrasound may result in a different estimated due date, particularly when the LMP is uncertain or menstrual cycles are irregular.

Early pregnancy ultrasound can be useful for establishing gestational age. Your healthcare professional will consider the available clinical information when determining the appropriate estimated due date.

You should not change your pregnancy dates based solely on an online calculator if your doctor or midwife has already provided a clinically established date.

What Does My Trimester Mean?

The calculator may also help identify which trimester you are currently in.

First Trimester

The first trimester covers the early stage of pregnancy and includes the initial weeks of fetal development.

Second Trimester

The second trimester is the middle portion of pregnancy. Pregnancy symptoms and physical changes may evolve during this period.

Third Trimester

The third trimester is the final stage leading toward delivery. Antenatal monitoring generally becomes increasingly important as the pregnancy progresses.

Why Should I Know My Estimated Due Date?

Knowing your estimated due date can help you understand your pregnancy timeline and keep track of important antenatal appointments and pregnancy milestones.

It can also provide a useful reference when discussing pregnancy progress with your healthcare professional.

However, the estimated date should always be treated as an approximate date rather than a guaranteed delivery day.

What If I Don't Remember My Last Period?

If you cannot remember the first day of your last menstrual period, do not simply guess a date if accuracy is important.

Your healthcare professional may use other information, including ultrasound findings, to estimate gestational age and establish an appropriate due date.

This is especially relevant when periods are irregular or the LMP is uncertain.

Important Note

The Pregnancy Due Date Calculator is intended for general informational and educational purposes. It should not replace professional medical assessment. If you are pregnant and have concerns about your pregnancy, gestational age, ultrasound findings, bleeding, pain, reduced fetal movement, or other symptoms, consult a qualified healthcare professional.

Key Takeaway

A Pregnancy Due Date Calculator provides a quick estimate of your expected delivery date using the first day of your last menstrual period. It can also help you understand your approximate pregnancy week and trimester. Because every pregnancy is different, the calculated date should be considered an estimate and confirmed or adjusted by your healthcare professional when necessary.