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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, 4.6 out of 5 based on 37 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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  • mercedes

    I would like to know is the day of conception the day you got pregnant or is it an estimate around the time you got pregnant cause me and my boyfriend broken up and i last had sex with him dec 14 2013 on the 19th i had sex with someone else but he didnt cum inside of me on the 20th me and my ex had sex my due date is sept 10th 2014 i am 8 weeks n 4 days thats what showed on my ultrasound somebody please help

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  • kesha

    If my due date is feb 28 2014 what day did I conceive on because my childs father thinks that its suppose to be in march that im due and I know that we had sex in the middle of june and my last period was may 24th 2013 please help me to expkain to him how this goes

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  • Nick

    My due date is July 27 2014 . My LMP was oct 20 2013 . It Went off Oct 26 2013 . I’m not sure if my sexual partner and I had sex between the 27 and 31 but i know I had sex with my ex boyfriend on nov 1 & 2 .. Could I possibly be pregnant by my ex boyfriend?

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  • shell

    Hiya :) my EDD is the 4.4.14 when did I conceive? Could it mean I could had sexual intercourse from the 8th and the sperm lived until about the 12-13th of july 2013? As I’m a tiny bit confused as to when was the latest I could have had intercourse to result in the sperm meeting the egg? Thank you so much xxx

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  • DeJanae

    I had sex with a guy on Dec 21st and my period came on the 11th of January like normal but it was very light compared to my other cycles which are unbelievably heavy. Here it is the 15 th of Feb and my period still has not came could I be pregnant?

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  • NK

    Hi this is my first pregnancy. I’m having a baby girl, I am now 36 weeks and 4 days. I had sex with a guy on May 18th, No condom, and I’m not on any type of birth control but I started my ovulation on the 19th or 20th. On June 1st, me and this other guy attempted to have sex but he didn’t go inside my vagina because it was hurting me. The doctor started my pregnancy on June 6th, 2013, I conceived about June 16-20th she says. I really don’t know whose the father, and it’s stressing be out. Please help me.

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  • Sarah

    How likely are you to get pregnant on your period?

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  • free

    My last menstrual. Was October 26 2013 when did I get pregnant

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  • confused

    If a woman had sex on May 19th, 2013 is there any way she could still be pregnant today (February 20th, 2014)

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  • jobs4michelles

    I have a question.. if I had intercourse on feb 2, 2014 and on feb, 21, I find out im 3 weeks does that mean the baby was conceived on the 2nd? Or was it earlier like late january?

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  • jobs4michelles

    Also when I took a pregnancy test this time it actually came out positive this time 2 days prior to my ultrasound on friday 21, 2014

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  • Kim lee

    If I had sex with my husband on July 27 2013 when will b my due date?

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  • Confused Mom

    I have a situation my due date was oct 22 2011 and I had a baby girl but thing about this situation is my child is very light-skinned and the guy I was dating is dark-skinned but I did have a relationship with another guy in the beginning of Feb and he is mixed so I know he can’t be the father (I’m brown-skinned). I’m so confused!

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  • terriah

    Hi I just found out I was pregnant on january 16,2014. I took a pregnancy test in December and January both came back negative. But my question is if I had sex with soomeone on December 1,2013 that was aone night stand, but withing that same week I had sex with my partner. I was scared because I wasnt sure if my partner was the father, but my doctor said I had to conceived within the 20-25 of December so im guessing my partner is the father. Can someone help me please????

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  • Anonymous

    If I had sex December 31 and January 4 and I had sex with another guy January 16th and I got a positive pregnancy test January 21 who baby is it ?

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  • Sandianne

    paternity test

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  • Sandianne

    again…paternity test

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  • Sandianne

    Im shocked at all the women on here with ridiculous questions…i.e. im pregnant and slept with 20 different guys, how do I find out who the father is-or- Im pregnant and my boyfriend left me and has a new girlfriend now, someone help us. Omg ladies, HELP yourselves. Stop putting yourself IN these positions in the first place. Obviously if you sleep around and un-protected at that, pregnancy is the least of your worries, but the obvious answer is a paternity test. Does it really matter when you conceived. Your doctor will date the pregnancy for you anyhow, knowing the first day of your last period is helpful, other than that, it doesn’t matter. I hate to be preachy, but go educate yourselves #mother of two * third on the way*,married, educated, MA,licensed radiology tech, CNA

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  • Rainelda

    i had sexual intercourse last february 13, 2013 and up to this day february 28, 2013 i don’t have a menstrual period. am i pregnant?

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  • Rainelda

    I had sexual intercourse with my husband on February 13, 2014. Up to this day my menstrual period is delayed. The first day of my last menstruation is on January 20, 2014

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  • sane

    saw may boyfriend on september 26 and we had unprotected sex , on september 27 i was on my period and we didnt have sex that day but on september 28 until october 4 we had unprotected sex . again had my period on october 14 and i hap protected sex with someonelse on october 20 it was a once of thing and later i found out that i was pregnant and i asked the other guy if the condom didnt break and he said no it didnt . Im scared and confused , im not sure who the father is

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  • nickyblu

    hi i need some help can anybody ask i had my last period on the 23 of sept 2013 and i started the mini pill because i had very bad periods i was on it for 2 weeks and 3 days i had sex with an ex boyfriend on the 1st of october and i came of the pill 2 days after because it was making me feel sick and a few days after i had sex with my boyfriend now am 23 weeks pregnant and i don’t ono who the father is am so scared and confused can someone help me or guide me thank you

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  • AA

    when did I conceive if the first day of my last menstrual period was February 10, 2014? If possible could I have conceived the day I had intercourse on February 20, 2014? What would be my due date?

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  • sally

    hi. I had sex oct 10th and 19th of 2013. ultrasound said, 8 in a half weeks on the 16th of dec. when was conception and when am I due?

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  • bubble_21

    Ok so I’m 19 weeks and 3 days pregnant my due date is August 11 , and im having trouble knowing who’s the father, I had sex with this one guy on October 22 and that’s it. Then another guy on November 8 soonest every other day. Who do you think might be the father.

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  • unknown

    I am 7weeks & 3days as of today pregnant. My due date has said to be November 8th, 2014. Can someone please help me with when I conceived. The conception calculater says around the 15th of February. Which is possibly right. but when I go back and subtract 3 months from February it will make my due date the end of November the beginning of December. So I’m really confused. Help. Please. Thanks in advance.

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  • Shania

    I found out that I’m four weeks pregnant on april3rd 2014, is it possible that I couldve conceived in january or its not.

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  • Hermione Jones

    try to remember who you slept with. if you have multiple sex partners then that would be the problem knowing your baby’s father

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  • Hermione Jones

    i hate to hear boys saying ..I’M sorry but the child is not mine..how can I stay away from such situation?

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  • harbormom4

    My sons ex says she’s pregnant with his baby. She says she’s due November 8. 2014, and supposedly conceived Feb 1,2014. They had sex the last time on january 31, 2014. She slept with his best friend on feb 11th and them someone else a week after that(feb17th). Who’s baby is it? She’s twlling people my son is the father. Please help me make some sense of this nightmare! !

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