About this tool
The estimate adds 280 days to the first day of your last period, then adjusts for cycle length: a longer cycle moves the date later, and a shorter cycle moves it earlier. This is known as Naegele's rule.
Pregnancy, Birth and Baby offers free calls with a maternal child health nurse on 1800 882 436, 7am to midnight (AET), 7 days.
Comparison: Pregnancy, Birth and Baby, Due date calculator, read on 12 October 2026.