Pregnancy Due Date Calculator
Calculate your pregnancy due date, current week, trimester, and key milestones using your last menstrual period (LMP) or conception date.
Pregnancy Details
Enter your last menstrual period date to calculate.
How It Works
Naegele's Rule adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. If you know your conception date, the calculator adds 266 days (38 weeks) instead. The result is your Estimated Due Date (EDD) — only about 5% of babies are born on their exact due date.
Naegele's Rule
Naegele's Rule: EDD = LMP + 280 days (40 weeks). Conception date method: EDD = Conception date + 266 days (38 weeks).
Pregnancy Trimesters
- First Trimester
- Weeks 1–12 — rapid cell division, organ formation, highest miscarriage risk
- Second Trimester
- Weeks 13–27 — most comfortable, baby movements begin, anatomy scan at week 20
- Third Trimester
- Weeks 28–40+ — rapid growth, lung maturation, preparation for birth
- Full Term
- 39 weeks 0 days to 40 weeks 6 days — optimal time for delivery
Frequently Asked Questions
How accurate is the due date calculator?
The LMP-based due date is an estimate. Only 5% of babies are born on their exact due date. Most births happen within 2 weeks before or after the EDD. An ultrasound in the first trimester (before 14 weeks) is more accurate for dating.
What are the three trimesters?
First trimester: weeks 1–12 (conception through end of month 3). Second trimester: weeks 13–27 (months 4–6, often the most comfortable). Third trimester: weeks 28–40+ (final months leading to delivery).
What if my cycle is not 28 days?
The standard Naegele's Rule assumes a 28-day cycle. If your cycle is longer (e.g. 35 days), ovulation occurs later, pushing the due date forward by the extra days. Your doctor will adjust the EDD based on ultrasound measurements.
When is a baby considered full term?
Full term is 39 to 40 weeks and 6 days. Early term is 37–38 weeks. Late term is 41–41 weeks 6 days. Post-term is 42 weeks or beyond. Babies born before 37 weeks are considered preterm.