If you need to know when you conceived, you are going to have the best chances of figuring out the precise date if:

  1. You have been tracking your monthly periods
  2. You have regular cycles

If you have a 28-day cycle, day 1 of your period is day 1 of your cycle.  Between days 14 and 16 of your cycle, you are the most fertile and most likely to get pregnant. You might want to find an online calculator to help you determine what date you conceived but you can often figure the conception date out manually quite easily.

Many women need to know this information so they can figure out their due date or figure out where they are in number of weeks pregnant.  If you’ve had multiple partners and are concerned about which partner is the baby’s father, you are most likely to figure out who you conceived with if you have been tracking your period.

If you aren’t sure how many weeks pregnant you are, your doctor can do a few things to help. Your doctor can check your HCG hormone levels through a blood test. The doctor is aware of specific ranges of hormone levels dictating the approximate gestation of the pregnancy. And, the doctor can also order an early ultrasound which allows the technician to measure the size of the embryo which can give you an estimated date of conception.


When this blog post was written several months ago I never intended to become a conception date guru so I may or may not be able to answer further questions on this post  as I’m getting hundreds of comments (many of which I’m not even approving due to the sheer volume) from people asking me who their baby’s father is. If your period is regular it’s often easy to tell the conception date. If you’ve had more than one partner within a few day span near to your ovulation date you need to do a paternity test. If your period is irregular, it’s difficult to tell.  Best of luck! If I do answer a question, please remember I’m NOT an expert and you’re encouraged to talk to your doctor or in some cases, seek out paternity testing. .  Inflammatory or spam comments will be deleted!

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192 Responses to “When Did I Get Pregnant? Manually Calculating Date of Conception”

  1. I wanna ask something my last period was on april 18 2011 I took a test on the 5 of may it said im not pregnant I took another one on the 11 also in the 18 but I had sex on the 11 going into the 12 of may but the 18 said no also and after that I had sex 19,20,21,22,23,

  2. When did I conseved