Pregnancy Due Date Calculator — EDD & Pregnancy Timeline
Calculation Method
About This Tool
The Pregnancy Due Date Calculator helps you estimate your baby's due date and track your pregnancy progress. By inputting the first day of your last period (LMP) or your conception date, you can map out a full week-by-week timeline of important physical milestones and trimester markers.
How to Use
- Choose either the Last Menstrual Period (LMP) or Conception Date method.
- Enter the date of your last period or date of conception.
- Adjust your average cycle length (if using the LMP method).
- Explore your customized trimester progress, estimated due date, and detailed week-by-week developmental timeline.
Detailed Explanation & Worked Example
An estimated due date (EDD) is a calculation that predicts when a pregnant woman will give birth. The standard pregnancy length is estimated to be approximately 40 weeks (280 days) from the first day of the last menstrual period (LMP) or 38 weeks (266 days) from the date of conception.
How is the Due Date Calculated?
The calculator supports two common methods of determination:
- Last Menstrual Period (LMP): Calculated using Naegele's Rule. This rule assumes a standard 28-day menstrual cycle. To calculate: add 280 days (9 months and 7 days) to the first day of your last period. If your average cycle is shorter or longer than 28 days, the calculator adjusts the date accordingly.
- Conception Date: If you track ovulation or underwent assisted reproductive technology (like IVF), you may know your exact conception date. In this case, the due date is calculated by adding 266 days to the conception date.
Pregnancy Milestones
Pregnancy is divided into three distinct phases called trimesters:
- First Trimester (Weeks 1 - 12): A time of rapid cellular development. Major organs start to form. The risk of miscarriage decreases after this period.
- Second Trimester (Weeks 13 - 27): Often called the "golden trimester" as morning sickness usually subsides. You can find out the baby's gender during the anatomy scan (around week 20) and start feeling movement.
- Third Trimester (Weeks 28 - 40): The baby continues growing rapidly to prepare for birth. Brain and lung development accelerate.