Due Date Calculator
Estimate your due date from the first day of your last period and your average cycle length. Your maternity care team may revise the date after an ultrasound.
Your pregnancy details
Your estimate
Enter your details to see an estimate.
How this estimate is calculated
The calculator uses a standard pregnancy dating convention: about 280 days from the first day of the last period. It adjusts that length by the difference between your cycle length and 28 days.
Pregnancy is dated from the last period, not from conception. The estimated conception date shown is therefore an approximation based on a typical cycle.
For the full method and the role of ultrasound dating, read how pregnancy due dates are calculated.
What this tool cannot tell you
- Whether the pregnancy is developing as expected
- Your baby’s health, size, or position
- The exact day you will give birth
- Whether you need medical care
Most babies are not born on the exact estimated due date. An early ultrasound can revise the date, and your care team’s estimate should take priority over this calculator.
Questions about due dates
How is a due date calculated?
A common method adds 280 days to the first day of the last period. Because that method assumes a 28-day cycle, this calculator adjusts the result if your average cycle is shorter or longer.
How accurate is an estimated due date?
It is a reference date, not a prediction of the exact birth day. Most babies are born in a range around the due date. An early ultrasound is often more accurate than a calendar estimate, especially if your cycles are irregular.
Can my due date change?
Yes. Your maternity care team may revise it based on an ultrasound or other information. Use the date they provide for appointments, leave planning, and decisions about your care.
General references
These organizations provide general health information. They are external sites with their own content and policies, and this site is not affiliated with them.