Due Date Calculator
Calculate your baby's due date.
Enter the first day of your last period (most common method)
Your estimated due date (EDD) is calculated as 280 days (40 weeks) from the first day of your last menstrual period. This method, known as Naegele's rule, has been used since the 1800s.
However, it's important to remember that your due date is an estimate, not a deadline. A normal pregnancy can last anywhere from 37 to 42 weeks. Only about 5% of babies are born on their exact due date!
First Trimester (Weeks 1-12)
Baby's organs form. You may experience morning sickness, fatigue, and breast tenderness. By week 12, baby is about 2 inches long.
Second Trimester (Weeks 13-26)
Often called the "honeymoon" phase. Energy returns, morning sickness eases. You'll feel baby's first movements and learn the sex (if you choose).
Third Trimester (Weeks 27-40)
Baby gains weight rapidly. You may feel more tired and experience Braxton Hicks contractions. Baby drops lower as due date approaches.
Regular prenatal care is essential for a healthy pregnancy:
- Week 8-10: First prenatal visit, dating ultrasound
- Week 11-14: First trimester screening (optional)
- Week 18-22: Anatomy scan ultrasound
- Week 24-28: Glucose screening test
- Week 36+: Weekly visits, Group B Strep test
Always consult your healthcare provider for personalized care recommendations.
Frequently Asked Questions
The due date is typically calculated as 280 days (40 weeks) from the first day of your last menstrual period (LMP). This is called Naegele's rule. However, only about 5% of babies are born on their exact due date—most arrive within two weeks before or after.
Gestational age is measured from the first day of your last period, while fetal age (also called embryonic age) starts from conception—about 2 weeks later. Medical professionals use gestational age because LMP date is usually more reliable.
First-trimester ultrasounds (before 13 weeks) are the most accurate, with a margin of error of about 5-7 days. Accuracy decreases as pregnancy progresses—second-trimester scans are accurate to within 10-14 days.
Yes, your due date may be adjusted if an early ultrasound shows a difference of more than 7 days from the LMP calculation. The ultrasound date is generally considered more accurate if done in the first trimester.
If you have irregular periods, the LMP method may not be accurate. An early ultrasound will give a more reliable estimate by measuring the baby's size. Dating by ultrasound is most accurate between 8-12 weeks.
Full term is 39-40 weeks. Early term is 37-38 weeks, late term is 41 weeks, and post-term is 42+ weeks. Babies born at or after 37 weeks are generally healthy, though research shows waiting until 39 weeks (if possible) provides the best outcomes.
Medical Disclaimer
This calculator provides an estimated due date based on standard calculations. Every pregnancy is unique, and your actual due date may vary. This tool is for informational purposes only and should not replace professional medical advice. Always consult with your healthcare provider for accurate dating and prenatal care.