Calculate your estimated due date (EDD) from your last menstrual period, conception date, or IVF transfer date. Includes your current pregnancy week, trimester dates, and a full pregnancy milestone timeline.
Your Pregnancy Timeline
Estimated Due Date—
Current Week—
Trimester—
Days Until Due Date—
Trimester Dates
Trimester
Weeks
Start Date
End Date
Key Pregnancy Milestones
Week
Date
Milestone
How the Due Date Is Calculated
Naegele's Rule (most common): EDD = LMP + 280 days (40 weeks). This assumes a 28-day cycle. If your cycle is longer, the EDD shifts later; shorter cycles shift it earlier.
Conception Date: EDD = Conception Date + 266 days (38 weeks). Conception typically occurs 14 days after LMP in a 28-day cycle.
IVF: For a Day 5 blastocyst transfer: EDD = Transfer Date + 261 days. For Day 3: EDD = Transfer Date + 263 days.
Important Notes
Only 5% of babies are born on their exact due date
Full-term is 39–40 weeks; 37–38 weeks is early-term
First-trimester ultrasound is the most accurate dating method
Always confirm your due date with your healthcare provider
How Due Dates Are Calculated
The standard method is Naegele's rule: take the first day of your LMP, add one year, subtract three months, and add seven days. This gives the estimated due date (EDD) at 40 weeks. The formula assumes a 28-day cycle; if yours is longer or shorter, your provider may adjust.
Only about 5% of babies are born on their exact due date. Most births occur within two weeks before or after the EDD. An early ultrasound (before 12 weeks) is more accurate than LMP for dating when cycle lengths are irregular.
Frequently Asked Questions
Your provider can estimate gestational age from an early ultrasound. Crown-rump length (CRL) at 8–12 weeks is the most accurate dating method. After 12 weeks, fetal measurements become more variable and less reliable for precise dating.
Full term is 39–40 weeks. Early term is 37–38 weeks; late term is 41 weeks; post-term is 42+. Babies born at 39–40 weeks generally have the best outcomes. Most providers recommend induction or monitoring by 41–42 weeks.
About 80% of births occur within 10 days of the EDD. First-time mothers tend to deliver slightly later (average 41 weeks + 1 day); subsequent pregnancies tend to come slightly earlier. Treat the EDD as a reference point for scheduling, not a precise prediction.
If your last menstrual period started on January 1, 2025, and you have a standard 28-day cycle: add 280 days to reach October 8, 2025 (your EDD). The first trimester ends around April 9, the anatomy scan would fall around May 28 (week 20), and full-term begins September 17 (week 39). If your cycle is 35 days instead of 28, shift the EDD 7 days later to October 15.
For IVF, the due date is calculated from the embryo transfer date rather than LMP. A Day 5 (blastocyst) transfer: add 261 days to the transfer date. A Day 3 (cleavage-stage) embryo: add 263 days. IVF due dates are generally more precise than LMP-based estimates because the fertilization date is known exactly, eliminating uncertainty about ovulation timing.