⏰ Estimated Due Date (EDD) Calculator — Free Online Tool

The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). If your cycle is longer/shorter than 28 days, the calculator automatically adjusts.

LMP-based due dates are accurate to ±2 weeks for most pregnancies. Only 4% of babies are born exactly on their due date. An ultrasound at 8–12 weeks provides the most accurate dating.

1st trimester: Weeks 1–13 (conception to 3 months). 2nd trimester: Weeks 14–27 (most comfortable period). 3rd trimester: Weeks 28–40 (preparation for birth). Full term begins at week 37.