How To Calculate Your Pregnancy 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 technique for doing so is in fact very different than you may think.

The standard method of calculating your due date is to add 280 days to the first day of your last menstrual period, or LMP.  Try out our handy pregnancy due date calculator to figure out your baby's 

estimated due date.

Enter the first day of your last menstrual cycle below:

Month: Day: Year:

Conception Date:
(Approximately two weeks after
your last menstrual period)
You are in your
First Trimester (wks. 1-12)
Maternity Health
Period of greatest risk for birth defects:
Five to ten weeks gestational age:

Stages of Pregnancy
Fetal organ formation:
Major organs have formed:

Beginning Second Trimester (12-27  weeks)
Risk of miscarriage decreases:

If your premature baby is due after this date,

s/he has a chance to survive
Childbirth Choices
Third Trimester
(27 weeks):
Your Due Date:
(40 weeks - full term):


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. Alternatively, you could use software which will not only track your ovulation cycle but also give you an estimated due date once you are pregnant.

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Now that you know your due date, talk with with other women due at the same time as you in the forum

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