Pregnancy Due Date Calculator
Calculate pregnancy due date
3 calculation methods
Week counter
Milestone timeline
Trimester tracker
The test is positive. Joy, excitement, and immediately: "When is the baby due?" Pregnancy is measured in weeks, but calculating from the last menstrual period to an estimated due date involves math that shouldn't be done while emotional.
This calculator estimates your due date, current week of pregnancy, and trimester—plus important milestones like when you might hear the heartbeat or feel movement. Take the guesswork out of pregnancy timing.
What is a Pregnancy Calculator?
A pregnancy calculator estimates the due date (Estimated Date of Delivery/EDD) based on the first day of your last menstrual period (LMP) or other known dates. Pregnancy is calculated as 40 weeks from LMP, though actual delivery typically occurs 38-42 weeks.
The calculation:
LMP: January 1, 2024
Due Date: October 8, 2024 (LMP + 280 days)
Conception: ~January 14 (LMP + ~14 days)
Note: Only ~5% of babies arrive on their due date
Early ultrasound measurements can adjust due dates more accurately than LMP calculations. If your ultrasound date differs significantly, use that instead.
Why People Actually Need This Tool
From the first prenatal appointment to maternity leave planning, accurate pregnancy dating affects dozens of decisions.
-
Due date estimation — Know when to expect your baby.
-
Prenatal care planning — Schedule appointments and tests at appropriate times.
-
Maternity leave timing — Plan work transitions around delivery.
-
Milestone tracking — Know when to expect heartbeat, movement, viability.
-
Trimester identification — Understand which phase you're in.
-
Medical conversations — Speak accurately with healthcare providers.
-
Preparation timeline — Plan nursery, purchases, and preparations.
How to Use the Pregnancy Calculator
-
Enter LMP date — First day of your last menstrual period.
-
Or enter conception date — If you know it precisely.
-
Or enter ultrasound date — With crown-rump length measurement.
-
View results — Due date, current week, trimester, and milestones.
| Milestone | Week | What to Expect |
|---|---|---|
| First prenatal visit | 6-8 | Confirm pregnancy, initial bloodwork |
| Heartbeat visible | 6-7 | Ultrasound can detect heartbeat |
| First trimester ends | 12 | Risk of miscarriage decreases |
| Anatomy scan | 18-22 | Detailed ultrasound, often learn sex |
| Feel movement | 18-25 | First-time moms: often later |
| Viability milestone | 24 | Medical intervention possible |
| Third trimester begins | 28 | Final growth phase |
| Full term | 37 | Safe to deliver |
| Due date | 40 | Estimated delivery date |
Only about 5% of babies arrive on their due date. The due "date" is really a due "week"—anywhere from 37-42 weeks is normal.
Real-World Use Cases
1. The Initial Due Date
Context: Positive pregnancy test, last period started January 1.
Problem: When is the baby due?
Solution: LMP January 1 + 280 days = October 8 due date. Currently ~5 weeks pregnant.
Outcome: Due date for planning, prenatal appointment scheduled.
2. The Ultrasound Adjustment
Context: Doctor says baby is measuring larger than LMP-based dates suggest.
Problem: Which due date is correct?
Solution: Early ultrasound is more accurate. Adjust due date based on measurements.
Outcome: Revised due date used for all future planning.
3. The Maternity Leave Planning
Context: Need to inform HR about leave timing.
Problem: How to plan around a date that's really a range?
Solution: Plan leave starting at 39 weeks. Have backup plan for earlier delivery.
Outcome: Work transition planned with flexibility built in.
4. The Viability Question
Context: High-risk pregnancy with concerns about premature delivery.
Problem: When does viability milestone occur?
Solution: 24 weeks is general viability threshold. Calculate that date.
Outcome: Important milestone date identified for medical planning.
5. The Anatomy Scan Scheduling
Context: Want to schedule 20-week anatomy scan.
Problem: When exactly is 20 weeks?
Solution: Calculate exact date range for 18-22 week window.
Outcome: Scan scheduled at optimal time for detailed views.
6. The Gender Reveal Planning
Context: Planning gender reveal party after anatomy scan.
Problem: When will scan be? How much time to plan party?
Solution: Anatomy scan at ~20 weeks. Schedule reveal 2 weeks later.
Outcome: Celebration timed appropriately after scan.
7. The Second Pregnancy Comparison
Context: Second pregnancy, wondering how timing compares to first.
Problem: First baby came at 38 weeks. What's that date this time?
Solution: Calculate 38-week date for planning purposes.
Outcome: Based on first pregnancy pattern, adjusted expectations.
Common Mistakes and How to Avoid Them
LMP calculations assume 28-day cycles with ovulation at day 14. Irregular cycles make this less accurate.
Privacy and Data Handling
This Pregnancy Calculator operates entirely in your browser.
- No dates are sent to any server.
- No pregnancy information is stored.
- No account required.
- Works completely offline.
Your pregnancy details stay private.
Conclusion
Pregnancy timing affects everything from medical care to life planning. Knowing your due date, current week, and trimester helps you navigate the journey with confidence.
This calculator turns dates into timelines. From initial due date calculation to milestone tracking, understand exactly where you are in the pregnancy journey.
Every week brings new developments. Know which week you're in.