Calculate Your Due Date

Now that you are pregnant, the first question most people will ask you is when you are due. Your health care provider may have already told you when your due date is, after confirming that you are in fact pregnant. It's fascinating how they determine this magical date, so let's go through exactly how they go about discovering just when you are due.

The standard method of calculating your due date is to add 280 days to the fist day of your last menstrual period, or LMP.

To figure out your due date simply indicate the date of your last menstrual period or (if known) the date of conception. It is important to note that the due date is just a guide as only 1 in 20 women actually delivery on their due date.

Last Menstrual Period (LMP)

Due Date    Days from Today   

Conception Date

Due Date   Days from Today

How this concept works: the 280-day cycle works on the typical 266-day gestation period plus 14 days, which would be the time from when you had your first day of your period, until the time when you would have more than likely ovulated. So you see this is not exact science. Why? Well, because this method assumes you would have ovulated exactly 14 days after you started your period and it assumes fertilization took place on that exact day.

There are other methods of calculating your due date of course. If you had been keeping track of your basal body temperature or your LH surge, you would know when ovulation occured, when you had intercourse and the date of conception. If you know this exact date for sure, then you would simply add the 266-day typical gestation period, and you would have your due date.