How to Calculate Conception Date

on Oct 24, 2012

by Lindsey Zaldivar

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How to Calculate Conception Date

How do you find out the day you conceived? Find out how to do the math and figure it out here.

When you find out that you’re pregnant, naturally the first thing you want to know is your due date! That is completely normal, since that is the exciting day that you will get to meet your little one! However, your next question might be what day you conceived. It sounds pretty simple right? Your conception date will be the day you had sex, right? Not so fast… Remember that sperm can live in the body for up to five days, so the day you had sex is not necessarily the date you conceived. Let’s explain how to figure out the date you conceived. Claim Your 20 Free Pregnancy Tests – Click Here

Figuring out your date of conception

If you have already been to the doctor, and know your expected due date, figuring out your date of conception is quick and easy! All you need to do is start with your due date, and count back 266 days. Simple as that! If that sounds like too much work to you, there are also a ton of online conception/due date calculators that will do all the work for you. So, if you know your due date already, it is a snap to figure out your date of conception. However, if you have not seen a doctor yet, and are trying to figure out your date of conception, it might be a little bit harder to figure out. If you have already been charting your cycles for ovulation purposes, figuring out your date of conception might be a bit easier. If you know when you ovulate, you know that your egg must be fertilized within 24 hours of ovulation, so that can narrow it down quite a bit for you.

Do the math!

However, this is how to determine an estimated date of conception if you haven’t been tracking your cycles. First of all, determine the date that you started your last period, and mark it down, if you haven’t already. Then add eleven days to the date your last period started. This is the first day that it was possible for you to conceive. Now, add another ten days to the first day that conception was possible. Those ten days are the days that it is possible for you to have conceived. You will have to narrow it down within those ten days to determine what your actual date of conception was.

Remember: conception dates are just estimates

Keep in mind, that just like due dates, conception dates are usually just estimates. You can sometimes pinpoint the exact date that you conceived, but not always. At least knowing your estimated date of conception will give you a better idea of when you conceived. As always, keep in mind that even if you do know your date of conception and your due date, it is no guarantee of when your baby will arrive. Babies come whenever they decide it’s time!

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How to Calculate Conception Date, 4.0 out of 5 based on 94 ratings

Lindsey lives in Roselle, Illinois with her husband and son Harry. In between keeping up with a busy toddler, she enjoys blogging about parenting, cooking, crafting at The Accidental Wallflower.

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  • Chloe

    I went to the doctor today and was told that my due date is September 16. That conception probably happened on December 24. I’m wondering if, then, the date of sex could have been December 19. It couldn’t be any sooner than that, right? I was also told today that I am a month along. How am I a month along if we conceived on December 24?

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  • mac

    I went through some stuff and I’m really ashamed of it but in Nov I went back to my ex and slept with him Nov 12th…I was on the last couple days of my period…Nov 16th I finally got together with my best friend and the love of my life I had a period in Dec from the 7th to the 10th, normal color normal flow…this month I got a negative pregnancy test 2 weeks ago and 3 positives this week…my mom said something today that has me freaking out…could this baby possibly be my ex’s?

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  • leah

    hi im 38 + 1 weeks today the last date of my period was april 21st 2106 but my cycles are never 28 days they are more …. I had unprotected sex on the 6 of may 2016 and then the following week I had unprotected sex again on the 15th of may when I went for my first scan they gave me my due date which is the 3rd feb 2017 so whos baby would it be ???
    ive used the conception calculators and they match the one for the 15may but I just wanted extra advise.

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