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Pregnancy Due Date Calculator

Estimate your due date using three methods: last menstrual period (Naegele's Rule), conception date, or ultrasound dating. Includes current gestational age, trimester tracking, pregnancy progress bar, and key milestone timeline.

Health

Calculation Method

First Day of Last Menstrual Period

Naegele's Rule: Due date is 280 days (40 weeks) from the first day of your LMP.

Understanding Your Pregnancy Due Date

A due date is an estimate of when your baby will be born, calculated as 40 weeks (280 days) from the first day of your last menstrual period. Only about 5% of births occur exactly on the due date. A full-term pregnancy ranges from 37 to 42 weeks.

Factors that affect due date accuracy:

Cycle length: Women with longer or shorter cycles may ovulate on a different day than the assumed day 14.
Ultrasound timing: First-trimester ultrasounds (weeks 8-13) are the most accurate for dating ±5-7 days.
Irregular cycles: Women with irregular periods may need adjustment based on ultrasound measurements.
Multiple pregnancies: Twins and multiples are typically delivered earlier than 40 weeks.

Pregnancy Timeline by Trimester

First Trimester

Weeks 1-13

Rapid development of all major organs and systems. Common symptoms include fatigue, nausea, and breast tenderness.

Second Trimester

Weeks 14-27

Baby grows significantly. Many women feel more energetic. Baby movements become noticeable.

Third Trimester

Weeks 28-40+

Baby gains weight and matures. The body prepares for labor. Braxton Hicks contractions may occur.

Pregnancy Milestones

Conception

Fertilization occurs, typically around week 2 of pregnancy.

Missed Period

Pregnancy test may show a positive result. HCG levels rise.

First Heartbeat

Baby's heart begins to beat. Visible on ultrasound.

Morning Sickness Peak

Nausea and fatigue are most common during this time.

12w

End of First Trimester

Risk of miscarriage drops significantly. Nausea often subsides.

16w

Movements May Begin

Some women feel the first fluttering movements (quickening).

20w

Anatomy Scan

Mid-pregnancy ultrasound checks baby's anatomy and development.

24w

Viability

Baby has a chance of survival outside the womb with medical support.

27w

End of Second Trimester

Baby can open and close eyes. Hearing is well developed.

28w

Third Trimester Begins

Baby gains weight rapidly. Brain and lungs continue maturing.

36w

Lightening (Baby Drops)

Baby moves into head-down position. Breathing becomes easier.

37w

Early Term

Baby is considered early term. Lungs are likely mature.

39w

Full Term

Baby is full term. Optimal time for delivery.

40w

Due Date

Estimated due date. Only about 5% of babies arrive exactly on their due date.

41w

Late Term

Induction may be recommended if labor hasn't started naturally.

Frequently Asked Questions

How accurate are due date calculations?▾

Due dates calculated from LMP have a margin of error of about 1-2 weeks. First-trimester ultrasound dating is the most accurate method (±5-7 days). Remember that a "normal" pregnancy can range from 37-42 weeks, so your baby may arrive earlier or later than the estimated date.

How is the due date calculated from ultrasound?▾

Ultrasound measures the baby's size (crown-rump length in first trimester, head circumference, femur length, and abdominal circumference in later trimesters) and compares it to standard growth charts to estimate gestational age. The due date is then calculated as 40 weeks from the estimated start of pregnancy.

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

Naegele's Rule assumes a 28-day cycle with ovulation on day 14. If your cycle is longer, you may ovulate later and your due date should be adjusted accordingly. For a 35-day cycle, add 7 days to the calculated due date. For a 21-day cycle, subtract 7 days. Your healthcare provider will typically use ultrasound dating for the most accurate estimate.

What does it mean if I go past my due date?▾

Going past 40 weeks is common — about 60% of first-time mothers deliver after 40 weeks. Post-term pregnancy is defined as 42+ weeks. Healthcare providers typically recommend additional monitoring starting at 41 weeks and may discuss induction between 41-42 weeks.

Do twins have a different due date?▾

Yes. Most twin pregnancies deliver between 34-37 weeks (vs 37-42 for singletons). The calculator provides a 40-week estimate based on standard dating, but your healthcare provider will adjust the expected delivery window based on the type of twins and overall pregnancy health.

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How to Use This Tool

Choose a calculation method: Last Menstrual Period, Conception Date, or Ultrasound.
Enter the required date(s) and gestational age if using ultrasound method.
View your estimated due date, current weeks pregnant, and trimester.
Check the pregnancy progress bar and upcoming milestone timeline.
Browse the educational sections for trimester information and FAQs.
Consult your healthcare provider for personalized medical advice.

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