Pregnancy Due Date Calculator

When will your baby arrive?

Enter your last menstrual period date or conception date to instantly calculate your due date, trimester, and how many weeks pregnant you are.

First day of your last menstrual period

Assumes a standard 28-day cycle. Due date = LMP + 280 days.

Understanding Your Due Date

A pregnancy due date (also called EDD — estimated date of delivery) is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is based on Naegele's Rule, the most widely used clinical method. Keep in mind that only about 5% of babies are born on their exact due date — most arrive within a 2-week window on either side.

Frequently Asked Questions

How is the pregnancy due date calculated?

The standard method adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is known as Naegele's Rule and is used by most OBGYNs worldwide.

How accurate is the due date calculator?

Only about 5% of babies are born on their exact due date. The due date is an estimate, and most births occur within 2 weeks before or after it. An ultrasound in the first trimester provides the most accurate dating.

What is a trimester?

A pregnancy is divided into three trimesters. The first trimester runs from weeks 1–13, the second from weeks 14–27, and the third from week 28 until birth around week 40.

Can I use the conception date instead of LMP?

Yes! If you know your conception date, our calculator adds 266 days (38 weeks) to it, since conception typically occurs about 14 days after the start of your LMP.

What if my cycle is irregular?

For irregular cycles, the LMP method may be less accurate. An early ultrasound (before 13 weeks) is the most reliable way to determine your due date when cycles are irregular.

What week does each trimester start?

The first trimester is weeks 1–13, the second trimester is weeks 14–27, and the third trimester begins at week 28 and continues until birth.