Pregnancy Due Date Calculator

How Due Dates Are Calculated

The estimated due date (EDD) is calculated by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP). This is known as Naegele's Rule and is the standard method used by healthcare providers.

Pregnancy Trimesters

• First Trimester: Weeks 1–12
• Second Trimester: Weeks 13–26
• Third Trimester: Weeks 27–40

Only about 4% of babies are born exactly on their due date. Most births occur within 2 weeks before or after. Always confirm your due date with your healthcare provider via ultrasound.