Due Date Calculator

The estimated due date (EDD) is the midpoint of a normal birth distribution, not an exact prediction. Normal term birth occurs between 38–42 weeks. Individual variation, genetics, first vs subsequent pregnancies, and fetal factors all influence timing. EDD is a planning target, not a precise event date.

First trimester ultrasound (8–13 weeks) is the most accurate dating method. If the ultrasound-estimated date differs from the LMP date by 7+ days in the first trimester, or 10+ days in the second, the ultrasound date is typically used. Later ultrasounds are less precise for dating due to natural variation in fetal size.

Irregular cycles make LMP-based calculation less reliable. If you track ovulation (via LH strips, BBT charting, or fertility monitoring), use the known ovulation date and add 266 days instead. Alternatively, use early ultrasound dating, which does not depend on cycle regularity.