Every month, typically 14 days before the first day of your period, one of your ovaries releases an egg (ovum). The sperm has somewhere between 24 and 48 hours to fertilize the egg. If the egg is not fertilized, conception does not occur and you will get your period on schedule. If you don't... congratulations! One of the first things you – and everyone else – will want to know is: when are you due?

Your health care provider will probably refer to that magic date as your EDD, meaning estimated due date (though it is also sometimes called the outdated term EDC – Estimated Date of Confinement). Keep in mind that this date is only an estimate.

The standard method to calculate your official due date is to count ahead 280 days from the first day of your last menstrual period (LMP). A second method for calculating your due date you can probably do in your head! Just take the date (day number) of your LMP and add 7, then subtract three months. For example:

LMP: April 14
Add 7: April 21 (14+7)
Count back 3 months: January 21

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