Free Due Date Calculator
Find out when your baby is due — using your last period date or your conception date
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How is due date calculated?
We use Naegele's Rule — the same formula your OB-GYN uses. It adds 280 days (40 weeks) to the first day of your last menstrual period. This accounts for the 2 weeks before conception in a standard 28-day cycle.
How accurate is this calculator?
This calculator gives you a reliable estimate. Only about 5% of babies are actually born on their exact due date. Most arrive within 2 weeks before or after. Your doctor will confirm with an ultrasound, especially in the first trimester.
What are the three trimesters?
Your pregnancy is divided into three trimesters. The first trimester is weeks 1–12, the second is weeks 13–27, and the third is weeks 28–40. Each trimester brings different development milestones and symptoms.
When should I see a doctor?
Book your first prenatal appointment as soon as you get a positive pregnancy test — ideally before week 8. Your doctor will confirm your due date with an early ultrasound and start your prenatal care plan.