Pregnancy Due Date Calculator
Find out when your little one is expected to arrive!
Calculate Your Due Date
Enter the first day of your last menstrual period (LMP)
Your Pregnancy Results
Pregnancy Progress
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This Week’s Milestones
How Is This Calculated?
What is Naegele’s Rule?
Naegele’s Rule is the standard method used by healthcare providers to estimate a due date. It works by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation occurring on day 14. The formula was developed by German obstetrician Franz Naegele in the early 1800s and remains the most widely used calculation method today.
How accurate is the due date calculation?
Only about 4-5% of babies are born on their exact due date. Most babies arrive within a two-week window around the estimated due date (between 38 and 42 weeks). Your healthcare provider may adjust your due date based on early ultrasound measurements, which can be more accurate, especially if your menstrual cycles are irregular.
What are the three trimesters?
First Trimester (Weeks 1-12): Major organs and structures begin forming. You may experience morning sickness and fatigue.
Second Trimester (Weeks 13-26): Often called the “golden period.” Baby grows rapidly and you may start feeling movements.
Third Trimester (Weeks 27-40): Baby gains weight and prepares for birth. You may experience Braxton Hicks contractions.
What if I don’t know my LMP date?
If you’re unsure of your last menstrual period date, your healthcare provider can estimate your due date using an early ultrasound. The most accurate dating ultrasounds are performed in the first trimester (before 13 weeks). Contact your OB-GYN or midwife for a proper assessment.
When should I see a doctor?
Schedule your first prenatal appointment as soon as you get a positive pregnancy test, ideally between 6-8 weeks. Regular prenatal care is essential for monitoring your health and your baby’s development throughout the pregnancy.
Medical Disclaimer
This pregnancy due date calculator is provided for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Every pregnancy is unique. Always consult your healthcare provider, OB-GYN, or midwife for accurate dating, personalized guidance, and any concerns about your pregnancy. If you experience any unusual symptoms, contact your healthcare provider immediately.
