Pregnancy Due Date Calculator

Estimate your delivery date using LMP or date of conception.

Your Estimated Due Date (EDD)

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Estimated Delivery Date (EDD)
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Estimated Conception Date
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Weeks of Pregnancy (Today)

Delivery Window

Delivery often occurs two weeks before or after the EDD.

Understanding Your Estimated Due Date (EDD)

The **Due Date Calculator** is one of the first and most critical tools used during pregnancy to set the **pregnancy timeline**. Your **Estimated Delivery Date (EDD)** is calculated primarily using the date of your **Last Menstrual Period (LMP)**, applying **Naegele's Rule**. This method assumes an average $28$-day cycle and a $40$-week gestational period. A secondary, more precise method uses the actual **date of conception**, if known.

Naegele's Rule and Conception Date Calculation

**Naegele's Rule**, the standard method for determining the **EDD**, is simple:

$$\text{EDD} = (\text{LMP} - 3 \text{ months}) + 7 \text{ days} + 1 \text{ year}$$

Alternatively, calculating the **EDD** from the **date of conception** involves adding $266$ days (38 weeks), as fertilization occurs roughly two weeks after the LMP. The calculator determines both the **Estimated Delivery Date** and the likely **conception date** for a full **pregnancy tracker** profile.

Accuracy and the Pregnancy Timeline

While the **Due Date Calculator** provides an accurate starting point for the **pregnancy timeline**, only about $4\%$ of babies are born exactly on their **EDD**. The **estimated delivery date** is a target, and delivery within two weeks before or after is considered normal. This tool is often verified by early ultrasound, which provides a more precise **EDD** by measuring the fetal growth rate.

Due Date Calculator FAQs

What is the difference between EDD based on LMP vs. Conception Date?

The **LMP** method (using **Naegele's Rule**) calculates the $40$-week **pregnancy timeline** from the start of your last period. The **conception date** method calculates the $38$-week timeline from the moment the egg was fertilized. They should result in nearly the same **Estimated Delivery Date (EDD)**.

Is Naegele's Rule always accurate?

**Naegele's Rule** assumes a perfect $28$-day cycle. If your **cycle length** is significantly shorter or longer, the prediction may be off. An early ultrasound is the most reliable method to confirm the **EDD** and refine the **pregnancy timeline** established by this **Due Date Calculator**.

How do I know my date of conception?

The **date of conception** is typically estimated to be the day of **ovulation**. If you have been using an **Ovulation Calculator** or basal body temperature (**BBT**) charting, you might have a precise **conception date**. Otherwise, the **Due Date Calculator** provides an estimate based on the LMP.