Health

Pregnancy Due Date Calculator

Estimate your baby's due date using Naegele's Rule from your last menstrual period (LMP) or a known conception date. Shows gestational age, trimester, and days remaining.

Enter a date above to calculate your estimated due date.

This calculator is for informational purposes only. Always consult your healthcare provider for medical advice.

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Naegele's Rule

From LMP

EDD = LMP + 280 days + (Cycle − 28)

From Conception

EDD = Conception Date + 266 days

Trimester Milestones

First Trimester (Weeks 1–12): Major organs begin forming. Highest risk of miscarriage. Nuchal translucency scan typically occurs at 11–14 weeks.

Second Trimester (Weeks 13–26): Fetal movement becomes noticeable. Anatomy scan (anomaly scan) usually at 18–22 weeks.

Third Trimester (Weeks 27–40):Rapid growth and preparation for birth. Most healthcare providers consider 37 weeks "early term" and 39–40 weeks "full term".

This calculator provides estimates for informational purposes only. Always consult your healthcare provider for personalised pregnancy care.

Frequently asked questions

How is the estimated due date (EDD) calculated?
The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). If your cycle is not 28 days, the date is adjusted by the difference from 28. For example, a 31-day cycle adds 3 days to the EDD.
How accurate is the due date estimate?
Naegele's Rule is a clinical estimate, not a guarantee. Only about 5% of babies are born on their exact due date. Most births occur within 2 weeks before or after the EDD. An ultrasound scan (especially in the first trimester) can refine the date based on fetal measurements.
What if my cycle length is irregular?
Irregular cycles make LMP-based estimates less reliable. If you know the approximate date of conception, use the conception date mode instead (EDD = Conception + 266 days). Your healthcare provider can also use early ultrasound for a more accurate dating.
What does gestational age mean?
Gestational age is measured from the first day of your LMP — not the date of conception. At the time of conception, you are technically considered 2 weeks pregnant by this convention. Full term is 40 weeks of gestational age (38 weeks post-conception).
When do the trimesters start and end?
The first trimester is weeks 1–12 (conception to week 12). The second trimester is weeks 13–26. The third trimester is weeks 27–40 (or birth). These boundaries are approximate and may vary slightly by practitioner or country.

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