How it works
How to calculate your due date.
Are you expecting? One of the first things you'll want to know is your due date. Only about 5% of babies are born on their exact due date, but having an estimate helps you and your provider plan the journey ahead.
What is an estimated due date?
An estimated due date (EDD) is the approximate day your baby is expected to arrive. It's typically calculated as 40 weeks from the start of your last menstrual period, or 38 weeks from conception. Remember — it's just an estimate. Your baby might arrive a little earlier or later.
First day of last period
The most common method used by healthcare providers: take the first day of your last menstrual period (LMP) and add 280 days (40 weeks). The standard formula assumes a 28-day cycle with ovulation on day 14 — your provider may adjust the date if your cycle is longer or shorter.
Conception date
If you tracked ovulation or used fertility treatments and know the date conception occurred, add 266 days (38 weeks). This can be more accurate when the conception date is well-established, but it's often harder to pinpoint precisely.
Every pregnancy is unique. Your baby will arrive when they're ready — and we'll be here whenever that is.