Due-date calculator

Enter the first day of your last period. The estimate appears in your browser — the date is never stored, sent, or saved anywhere.

How it works

The standard estimate (Naegele's rule, per ACOG patient education) adds 280 days — 40 weeks — to the first day of the last menstrual period, adjusted when a typical cycle is longer or shorter than 28 days. A due date is a planning estimate: only a small minority of babies are born on the exact day, and your provider's dating — especially an early ultrasound — outranks any calculator, including this one.

Educational information only — not medical advice. Every pregnancy and every baby develops on their own timeline. If you have any concern, talk to your obstetric provider or your baby's pediatrician.