Pregnancy Due Date Calculator

Enter your last menstrual period or conception date to calculate your estimated due date. Track your pregnancy week and trimester.

Select the date your last period started

Use 28 days (default) if unsure

Frequently Asked Questions

How is the due date calculated?
Using Naegele's rule, 280 days (40 weeks) are added to the first day of your last menstrual period. This is based on an average pregnancy duration.
How accurate is the estimated due date?
Only about 5% of babies are born on their exact due date. Most births occur within 2 weeks before or after the estimated date.
What are pregnancy trimesters?
Pregnancy is divided into three trimesters: first (weeks 1-12), second (weeks 13-27), and third (weeks 28-40). Each has different developmental milestones.
Updated 2026 — WHO standards