Pregnancy Calculator | Due Date & Gestational Age Estimator

📖 How to Use This Pregnancy Calculator

Select your calculation method - Choose from LMP, Conception Date, or Known Due Date.

Enter the date - Input your LMP, conception date, or known due date.

Click "Calculate Pregnancy" - Get your due date, gestational age, trimester, and days remaining.

🤰 Understanding Pregnancy Calculation

A full-term pregnancy typically lasts about 280 days (40 weeks) from the first day of your last menstrual period (LMP). This is known as Naegele's Rule. Conception usually occurs around day 14 of a 28-day cycle, which is why due dates are calculated 40 weeks from LMP but only 38 weeks from conception.

Only about 4-5% of babies are born exactly on their due date. Most arrive between 37 and 42 weeks. First-trimester ultrasounds provide the most accurate dating (within 3-5 days).

📊 Calculation Methods Explained

LMP Method: Due Date = LMP + 280 days (40 weeks). Most common method for women with regular 28-day cycles.
Conception Date Method: Due Date = Conception Date + 266 days (38 weeks). Useful when conception date is known (IVF or tracked ovulation).
Due Date Method: Enter known due date to calculate current gestational age and conception date.

📅 Pregnancy Trimesters at a Glance

First Trimester (Weeks 1-12): Morning sickness, fatigue, hormonal changes. Baby's major organs form. First ultrasound at 8-12 weeks.
Second Trimester (Weeks 13-26): Energy returns, baby movement felt (quickening at 18-22 weeks). Anatomy scan at 18-22 weeks.
Third Trimester (Weeks 27-40): Baby grows rapidly, prepare for delivery. Braxton Hicks contractions may occur. Hospital bag preparation at 36+ weeks.

💡 Important Pregnancy Milestones

Week 6-8: First heartbeat detected via ultrasound
Week 10-12: Nuchal translucency screening for chromosomal abnormalities
Week 16-20: Anatomy scan to check baby's development
Week 24-28: Gestational diabetes screening
Week 36-37: Group B Strep screening
Week 39-41: Full term - baby can arrive any day

❓ Frequently Asked Questions (FAQ)

How accurate is the pregnancy calculator?

Calculations based on LMP have an accuracy of ±7-10 days. First-trimester ultrasound (8-12 weeks) is most accurate, with ±3-5 days accuracy. Only about 5% of babies are born on their exact due date.

What if my cycle is longer or shorter than 28 days?

For cycles longer than 28 days, ovulation occurs later - add the difference to your due date. For shorter cycles, subtract the difference. For example, a 35-day cycle would add 7 days to the due date.

When does morning sickness typically start?

Morning sickness usually begins around week 6 of pregnancy and peaks around week 9. It typically resolves by weeks 12-14, though some women experience it longer.

When can I feel the baby move?

Most women feel the first fetal movements (quickening) between 18-22 weeks. First-time mothers may feel movement later, while experienced mothers may feel it earlier.

What is considered full term?

Early term: 37-38 weeks; Full term: 39-40 weeks; Late term: 41 weeks; Post-term: 42+ weeks. Babies born at 39-40 weeks have the best health outcomes.

How does ultrasound dating compare to LMP dating?

Early ultrasounds (8-12 weeks) measure the baby's crown-rump length for accurate dating. If there's a discrepancy of more than 5-7 days from LMP, the ultrasound date is typically used for calculating due date.