Pregnancy Week Calculator

This adds 280 days to the first day of the last period. Error is larger when cycles differ from 28 days or the date is uncertain. Prenatal clinicians establish gestational age and due date from early ultrasound and records; this calculation does not replace the clinical due date.

For heavy bleeding, severe abdominal pain, trouble breathing, fainting, severe headache or vision change, sudden major swelling, or reduced fetal movement, stop and contact obstetric or emergency care now.