Pregnancy due date
Estimated due date and current week from a last period or conception date.
An estimate — only a clinician can date a pregnancy properly.
28 is the standard assumption
220 days away
First trimester
37 weeks
Milestones
| Week | Milestone | Date |
|---|---|---|
| 12 | End of the first trimester | Aug 21, 2026 |
| 20 | Halfway — anatomy scan around now | Oct 16, 2026 |
| 24 | Viability threshold | Nov 13, 2026 |
| 28 | Third trimester begins | Dec 11, 2026 |
| 37 | Full term begins | Feb 12, 2027 |
| 40 | Due date | Mar 5, 2027 |
| 42 | Post-term | Mar 19, 2027 |
How it works
Pregnancy is dated from the first day of the last menstrual period, not from conception — which means the first two weeks of a “pregnancy” precede it. That convention exists because the period is a date people can report reliably and ovulation is not.
Naegele's rule: due date = LMP + 280 days
(adjusted by cycle length − 28)
From conception: due date = conception + 266 days Cycle length matters
Naegele's rule assumes ovulation on day 14 of a 28-day cycle. Someone with a 35-day cycle typically ovulates around day 21, pushing the due date a week later. This calculator adjusts for that; many do not.
Term is a range, not a date
Since 2013, obstetric guidance has split the old “term” into early term (37–38 weeks), full term (39–40), late term (41) and post-term (42+). Outcomes are best in the full-term window, which is why elective delivery before 39 weeks is now discouraged without a medical reason.
Sources
Naegele's rule as described in standard obstetric practice; term definitions from the American College of Obstetricians and Gynecologists (ACOG) Committee Opinion 579, reaffirmed. This is an educational estimate — clinical dating supersedes it.