Pregnancy Due Date Calculator
Estimated due date from your last menstrual period.
How the due date is estimated
The standard clinical method (Naegele's rule) adds 280 days — 40 weeks — to the first day of your last menstrual period. The tool also shows how many weeks pregnant you are today and your current trimester.
How accurate is it?
Only about 1 in 20 babies arrives on the exact due date; most are born within two weeks either side. An early ultrasound gives the most accurate dating — always confirm with your healthcare provider.
Frequently asked questions
What if my cycles are irregular?
The LMP method assumes a 28-day cycle. With irregular cycles, ultrasound dating from your provider is much more reliable.