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What is Pregnancy Due Date Calculator?

Free pregnancy due date calculator. Enter your last menstrual period, conception date, or ultrasound date to get your estimated due date, current week, trimester, and week-by-week milestones. For informational use only — always consult your OB-GYN.

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Free Pregnancy Due Date Calculator

Calculate your estimated due date three ways: from your last menstrual period (Naegele's rule), from a known conception date, or from an ultrasound date plus gestational age. See your current pregnancy week and day, your trimester, and a week-by-week milestone timeline. For informational use only — not a substitute for professional obstetric care.

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⚠️ For informational use only — not medical advice

Due date estimates are approximations. Always confirm your due date with your OB-GYN or midwife via ultrasound. This tool does not replace professional obstetric care.

Estimated due date

February 7, 2027

280 days to go

Current gestational age

0w 0d

weeks + days pregnant

Trimester

1st

Weeks 1–12

Key dates

Est. conception dateMay 17, 2026
End of 1st trimesterJuly 26, 2026
End of 2nd trimesterNovember 1, 2026
Full term begins (39w)January 31, 2027
Due date (40w)February 7, 2027
💧Water intakeAdjust for pregnancy🔥Calorie calculatorPrenatal nutrition🍽️Meal ideasrowgress.com/meals

Reminder: This calculator provides estimates for informational purposes only. It is not a substitute for professional medical advice. Always consult your OB-GYN or midwife regarding your pregnancy.

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Frequently Asked Questions

The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14. For cycles longer or shorter than 28 days, the actual ovulation date — and therefore conception date — shifts, making ultrasound dating more accurate in those cases.
Only about 5% of babies are born on their exact due date. A first-trimester ultrasound (before 14 weeks) is the most accurate dating method, typically accurate to within 5–7 days. LMP-based dating is accurate to within 1–2 weeks for women with regular 28-day cycles. Due dates are best understood as the center of a 2-week window (38–42 weeks gestation is considered full term).
Pregnancy is divided into three trimesters. The first trimester is weeks 1–12. The second trimester is weeks 13–26. The third trimester is weeks 27–40 (and beyond). Each trimester has distinct developmental milestones and common symptoms. Most miscarriage risk is concentrated in the first trimester; risk drops significantly after week 12.
Gestational age is the age of the pregnancy measured from the first day of the last menstrual period — not from conception. This means gestational age at conception is typically around 2 weeks. A full-term pregnancy is 40 weeks gestational age. Ultrasound measurements (crown-rump length in the first trimester, biometric measurements later) are compared to gestational age norms to confirm or adjust the due date.
No. This calculator is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Due date estimates should always be confirmed by an obstetric provider, typically via ultrasound. If you have any concerns about your pregnancy, contact your OB-GYN or midwife.

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How Due Dates Are Calculated

The standard method for estimating a due date is Naegele's rule, developed by German obstetrician Franz Karl Naegele in 1812: add 280 days (40 weeks) to the first day of the last menstrual period. This assumes a 28-day cycle with ovulation on day 14. The formula has been used for over two centuries and remains the clinical default, though it is acknowledged to be an approximation.

When Ultrasound Dating Differs from LMP Dating

When first-trimester ultrasound measurements differ from LMP-based dating by more than 5–7 days, most obstetric guidelines recommend adjusting the due date to match the ultrasound. Crown-rump length (CRL) before 14 weeks is the most accurate ultrasound dating measure. After 14 weeks, dating accuracy decreases because individual variation in fetal size increases. If your ultrasound date and LMP date conflict, defer to your OB-GYN — they will assess which is more reliable for your specific situation.

Full Term and Preterm Definitions

The American College of Obstetricians and Gynecologists (ACOG) defines the following gestational age milestones: preterm (before 37 weeks), early term (37–38 weeks 6 days), full term (39–40 weeks 6 days), late term (41–41 weeks 6 days), and post-term (42 weeks and beyond). The risk of complications is lowest between 39 and 40 weeks 6 days — this is the full-term window your due date falls within.

Prenatal Nutrition During Pregnancy

Calorie and nutrient needs increase during pregnancy. Most guidelines recommend an additional ~300 calories per day in the second and third trimesters. For general nutrition planning and calorie targets, see the TDEE & Calorie Calculator. For hydration guidance, see the Water Intake Calculator — fluid needs also increase during pregnancy. Always discuss specific dietary changes with your OB-GYN or a registered dietitian.