How pregnancy due date calculator works
Your estimated due date (EDD) is calculated from the first day of your last menstrual period (LMP). Naegele’s rule adds 280 days (40 weeks) to the LMP, because ovulation and conception typically happen around day 14 of a 28-day cycle and pregnancy lasts about 266 days from conception. Enter your LMP and cycle length and the tool does the rest.
Cycle length matters. If your cycles are longer or shorter than 28 days, ovulation shifts, and so does your due date. This calculator adjusts the due date by your cycle length minus 28 days, so a 32-day cycle pushes the due date four days later. You can also switch to the conception-date method, which adds 266 days to the date you conceived.
The tool reports your gestational age (how many weeks and days pregnant you are today), your current trimester, the days remaining until your due date, and a milestone timeline — the end of the first trimester (13 weeks), the earliest viability (24 weeks), the start of the third trimester (28 weeks), early term (37 weeks), and full term (40 weeks). This is an estimate for education only and not medical advice; only about 5% of babies arrive on their exact due date.