How to Use the Pregnancy Calculator
Enter your last menstrual period (LMP) date or conception date. The calculator shows estimated due date, current week of pregnancy, trimester, and key milestones.
Pregnancy Calculator Formula
Due Date = LMP + 280 days (Naegele's rule)Trimesters= T1: weeks 1–13 | T2: weeks 14–27 | T3: weeks 28+
Example Calculation
LMP: 1 January 2025:
Due date = 1 Jan + 280 days
Due date: 8 October 2025; Full term from 16 Sep 2025 (week 37)
Frequently Asked Questions
How accurate is the due date?
Only about 5% of babies are born on their due date. The estimated due date (Naegele's rule: LMP + 280 days) has an accuracy range of ±2 weeks. An ultrasound in the first trimester is the most accurate dating method.