Due Date Calculator

The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This remains the most widely used calculation worldwide, though ultrasound dating — especially before 14 weeks — can be more accurate for irregular cycles.

Only about 4–5% of babies are born on their exact due date. Most are born within 2 weeks before or after. The EDD is best understood as the midpoint of a normal delivery window (37–42 weeks). Accuracy also depends on cycle regularity — irregular cycles can shift the date by 1–2 weeks.

Yes. If your dating ultrasound (typically at 8–14 weeks) shows a significant size difference from what LMP predicts, your provider may revise the EDD. Changes of 5–7 days or more often prompt a revision earlier in pregnancy; later ultrasounds are less reliable for dating purposes.

The American College of Obstetricians and Gynecologists (ACOG) defines full term as 39 weeks 0 days through 40 weeks 6 days. Early term is 37–38 weeks. Late term is 41 weeks. Post-term is 42 weeks and beyond, when induction is typically discussed.

Most guidelines recommend offering induction at 41–42 weeks. ACOG recommends discussing induction at 41 weeks and strongly advises against going past 42 weeks. Your provider will monitor fetal wellbeing and amniotic fluid levels in this period.