Estimate your due date, current week, and key pregnancy milestones
Estimate using Naegele's rule (LMP + 280 days, adjusted for cycle length). Only about 5% of babies are born on the estimated due date. If your ultrasound dating differs from LMP dating, your clinician's date takes precedence (ACOG). Not medical advice.
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Frequently Asked Questions
The standard method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14.
Gestational age is the age of the pregnancy measured from the first day of the last menstrual period. It is typically about 2 weeks more than the actual embryo age, because conception happens about 2 weeks after menstruation begins.
Only about 4% of babies are born on their exact due date. 80% arrive within two weeks before or after. First-trimester ultrasounds are more accurate than the LMP method.