Due Date
Calculate pregnancy due date and milestones
These calculators provide general information only and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How to use Due Date
- 1Enter the first day of your last menstrual period (LMP).
- 2The tool adds the standard 280 days (40 weeks) to estimate the due date.
- 3See due date, current week, and key prenatal checkup milestones.
How due date is calculated: LMP and weeks
due = LMP + 280 days (Naegele: month+9, day+7)The common method is Naegele's rule: from the first day of LMP, add 280 days (40 weeks). The shortcut is 'month+9, day+7'.
Only about 5% deliver exactly on the due date; within two weeks either side is normal. Early ultrasound (esp. CRL) refines the week better.
The tool also shows current gestational week and key screenings (NT, anatomy, glucose) so you can map the whole pregnancy timeline.
Frequently asked questions
Is the due date accurate?
It's a midpoint estimate. ~80% are born within two weeks of it; only ~5% on the exact day. Treat it as a window, not a date.
Irregular cycles?
Long or irregular cycles make LMP-based dating early. First-trimester ultrasound (CRL) is more accurate.
Why weeks, not months?
Weeks (7-day) are finer; screenings are scheduled by week (NT 11–13, glucose 24–28), so weeks avoid missing windows.