Due date calculator
Enter the first day of your last period to see your estimated due date and how many weeks along you are.
When is the baby due?
How it is worked out
The due date is found by adding 280 days (40 weeks) to the first day of your last period. This is called Naegele's rule, and it assumes a cycle of about 28 days.
If your cycle is longer or shorter, or you are not sure of the date, a first-trimester scan usually gives a more accurate date. Your doctor or midwife may adjust it based on that scan.
How exact is it?
Only a small share of babies arrive on their due date. A pregnancy counts as full term when the baby is born between 37 and 42 weeks, so the date is a guide rather than a deadline.
Common questions
What if my cycle is not 28 days?
The calculator assumes an average cycle. With a longer cycle the birth may come a little later, and the other way round. An early scan makes the date more precise.
Is the date I enter saved?
No. The calculation is just for you and is not stored anywhere.