Pregnancy Due Date Calculator

Understanding Your Due Date

Your estimated due date (EDD) marks the end of the typical 40-week pregnancy. It's calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. While called a "due date," it's actually an estimate - only about 5% of babies arrive on their exact due date. Most babies (80%) arrive within two weeks before or after the estimated date.

How Pregnancy is Counted

Pregnancy is counted from the first day of your last period, not from conception. This might seem odd, but it's standard medical practice because most women know their period date but not the exact conception date. Conception typically occurs about 2 weeks after your period starts (during ovulation), so you're technically "pregnant" for 2 weeks before conception even occurs in this counting system.

The Three Trimesters

First Trimester (Weeks 1-13): The most critical development period. By week 8, all major organs are forming. Morning sickness, fatigue, and breast tenderness are common. Miscarriage risk is highest during this trimester.

Second Trimester (Weeks 14-27): Often called the "golden trimester" as morning sickness typically subsides and energy returns. You'll feel baby's first movements (quickening) around weeks 18-25. The 20-week anatomy scan checks baby's development.

Third Trimester (Weeks 28-40): Baby gains weight rapidly. You may experience more discomfort as baby grows. Braxton Hicks contractions (practice contractions) become noticeable. Baby typically moves into head-down position by week 36.

Important Pregnancy Milestones

• Week 4-5: Pregnancy test turns positive
• Week 6-8: First ultrasound detects heartbeat
• Week 12: End of first trimester, miscarriage risk drops significantly
• Week 20: Anatomy scan, can often determine baby's sex
• Week 24: Viability - baby could potentially survive if born prematurely
• Week 28: Third trimester begins
• Week 37: Full term - baby is ready to be born safely

When Will Your Baby Actually Arrive?

While 40 weeks is considered full term, babies born anywhere from 37-42 weeks are considered normal. First-time mothers tend to deliver slightly later (average 40 weeks + 5 days), while subsequent pregnancies often deliver earlier. Your doctor will monitor you closely after 40 weeks and may discuss induction if you go significantly past your due date.

Frequently Asked Questions

How is due date calculated?

Due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is Naegele's Rule, used by healthcare providers worldwide.

How accurate is the due date?

Only 5% of babies arrive exactly on their due date. Most babies (80%) arrive within 2 weeks before or after the due date. It's an estimate, not a guarantee.

When does each trimester start?

First trimester: Weeks 1-13. Second trimester: Weeks 14-27. Third trimester: Weeks 28-40. Each trimester brings different developmental milestones and physical changes.

Can my due date change?

Yes, early ultrasound measurements (before 13 weeks) are more accurate than LMP dating. Your doctor may adjust your due date based on ultrasound findings.

When will I feel the baby move?

First-time mothers typically feel movement (quickening) between weeks 18-25. Second-time mothers may feel it earlier, around weeks 16-18, as they recognize the sensation.