The Due Date Calculator estimates your baby's expected delivery date based on the first day of your last menstrual period (LMP) or conception date. It also shows your current week of pregnancy and trimester, and provides a timeline of key pregnancy milestones.
How the Formula Works
Naegele's Rule: Due Date = LMP + 280 days (40 weeks). From conception: Due Date = Conception Date + 266 days (38 weeks).
How to Use This Calculator
Enter the first day of your last menstrual period, or
Enter the estimated conception date
View your estimated due date and current pregnancy week
Tips & Best Practices
Only about 5% of babies are born on their exact due date — it's an estimate
Full term is considered 39–40 weeks; early term is 37–38 weeks
First-time mothers tend to deliver slightly later than their due date on average
An ultrasound in the first trimester is the most accurate way to confirm your due date
Important Limitations
Assumes a 28-day menstrual cycle with ovulation on day 14 — cycles vary
Not accurate for women with irregular periods
Ultrasound dating may differ from LMP-based calculations