Find your estimated due date, current pregnancy week, trimester, and key milestones. Enter your last period, conception date, or IVF transfer date.
First Day of Last Period
Estimated Due Date
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Weeks pregnant
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Days pregnant
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Trimester
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Days until due date
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Weeks remaining
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Conceived ~week
Pregnancy Progress
Week 1Week 13Week 28Week 40
1st Trimester (Wks 1–12)
2nd Trimester (Wks 13–27)
3rd Trimester (Wks 28–40)
Key Milestones
⚕️ Medical disclaimer: This calculator provides estimates only. Due dates can shift based on ultrasound measurements. Always confirm your due date with a healthcare provider.
How to Use This Calculator
1
Choose your calculation method — Last Period (LMP) is the most common. Use Conception Date if you know when you conceived. Use IVF Transfer for assisted reproduction.
2
Enter your date and adjust cycle length if your cycles are not the standard 28 days.
3
View your due date and milestone timeline — including key scan dates, trimester transitions, and viability milestones.
4
Confirm with your doctor — early ultrasound (before 14 weeks) is the most accurate way to confirm gestational age.
How Pregnancy Due Dates Are Calculated
A full-term pregnancy lasts approximately 40 weeks from the first day of the last menstrual period (LMP) — not from conception. This standard, known as Naegele's Rule, adds 280 days (40 weeks) to the first day of the LMP. The reason it's measured from LMP rather than conception is practical: conception date is rarely known with precision, but the start of a period is a clear, memorable event.
The Three Trimesters
Pregnancy is divided into three trimesters of roughly 13 weeks each. The first trimester (weeks 1-13) covers early development and is when the risk of miscarriage is highest. The second trimester (weeks 14-27) is typically the most comfortable period — morning sickness often subsides and energy returns. The third trimester (weeks 28-40) involves rapid fetal growth and preparation for birth. Most pregnancies deliver between 37 and 42 weeks.
Due Date Accuracy
Only about 5% of babies are born on their exact due date. The due date is best understood as the midpoint of a normal delivery window — roughly 2 weeks before or after. A first-trimester ultrasound (typically performed between 8-12 weeks) provides the most accurate due date estimation by measuring the fetal crown-rump length. If the ultrasound date differs from the LMP calculation by more than a week, OBs typically adjust the due date to the ultrasound estimate.
This calculator provides an estimated due date based on LMP or conception date. All pregnancy calculators produce estimates — your healthcare provider will establish your official due date and gestational age based on clinical examination and ultrasound findings. Always follow your provider's guidance for prenatal care schedules.
Frequently Asked Questions
How is the due date calculated?
The standard method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last period. If you know your conception date, we add 266 days. IVF transfers use specific adjustments based on embryo age.
How accurate is a due date?
Only about 5% of babies arrive on their exact due date. Most are born within 2 weeks before or after. Early ultrasounds (before 14 weeks) are the most accurate way to confirm your due date.
What are the three trimesters?
The first trimester runs from week 1 to 12. The second from week 13 to 27. The third from week 28 to 40 (or delivery). Full term is considered 39–40 weeks.
What is a full term pregnancy?
The American College of Obstetricians defines full term as 39 weeks 0 days to 40 weeks 6 days. Early term is 37–38 weeks. Late term is 41 weeks. Post-term is 42+ weeks.
When should I see a doctor?
Schedule your first prenatal appointment as soon as you have a positive pregnancy test, ideally before 10 weeks. Regular prenatal visits are essential to monitor your health and your baby's development.