Pregnancy Due Date Calculator
Calculate your estimated due date (EDD) from the first day of your last menstrual period (LMP).
How to use this tool
- Enter first day of last period in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your estimated due date and the full breakdown beneath it.
Add 280 days (40 weeks) to the first day of your last menstrual period to get your estimated due date. This is the Naegele's rule calculation.
Frequently asked questions
- How accurate is this due date calculation?
- Only about 5% of babies are born on their exact due date. Most arrive within two weeks either side. An ultrasound gives a more precise estimate.
- What if I don't know my LMP?
- An early ultrasound (ideally at 8–12 weeks) can establish gestational age and give a reliable due date even without a known LMP.