Calculate from your last period or conception date — with trimester timeline and milestones
A pregnancy due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period — known as Naegele's Rule. If your last period started January 1 your estimated due date is October 8. Only 5% of babies are born on their exact due date. Most arrive within two weeks before or after. Full term is 39 to 40 weeks.
An estimated due date (EDD) marks the end of the 40th week of pregnancy counted from the first day of your last menstrual period. Pregnancy is divided into three trimesters: first (weeks 1–12) second (weeks 13–26) and third (weeks 27–40). Your healthcare provider may adjust your due date based on ultrasound measurements. This calculator is for informational purposes only — always consult your doctor.
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