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Table of Contents
- What is a Conception Calculator
- How Does It Work?
- How is the Conception Date Calculated and What is it Based On?
- Facts about Conception
- Calculating based on your Estimated Due Date
- Calculating Based on your LMP
- Calculating Based on Ovulation Dates/Fertile Period
- Calculating Based on your Ultrasound
- What Can Affect Conception Dates
- Is the conception calculator practical?
- FAQ’s
What is a Conception Calculator
A pregnancy conception calculator can help you determine when your baby was conceived, based on a few different factors such as the first date of your last menstrual period (LMP), the due date of your baby, or when the baby was actually born.
The pregnancy conception calculator estimates the date of conception according to the anticipated due date of pregnancy. The calculator also quotes a possible selection of days where sexual intercourse may have resulted in conception according to the fact that sperm lives for 3-5 days inside a female’s body.
Whichever method you choose to use in order to determine the date of conception, it will give you a range (which will coincide with your fertile period) to go by.
You can input the information into the conception calculator below in order to come up with that time-frame. This is when knowing when your period started is important, especially if you haven’t been to the doctor yet.
from Birth, LMP and Due dates.
These estimated conception dates are based on an average cycle of 28 days.
To use the calculator:
These estimated conception dates are based on an average cycle of 28 days, which is what most calculators are based on.
While we are aware that some people have a longer or shorter cycle, an average of 28 days is used while calculating the date of conception.
How Does It Work?
The conception calculator figures the gestational age of the baby to determine the date of conception. Since the exact date of conception is hardly ever known, the conception calculator can use the first day of the last menstrual period (LMP) you have to determine the range of days in which conception would have occurred.
You can also use the conception calculator if you know the due date of your baby. The baby can typically be dated 5 or 6 weeks after your last menstrual period to determine the gestational age of the baby and the approximate due date.
If you know either of these figures, you can input this information into the conception calculator along with the current date to find out the possible days of conception.
Again, the conception calculator bases this off of the average 28-day cycle. If you have a shorter or longer cycle you will have to account for that manually, moving the range over a few days in either direction so to speak.
How is the Conception Date Calculated and What is it Based On?
This process is based on a typical, textbook pregnancy. This means that we calculate it based on a pregnancy that lasts 40 weeks in woman with a 28-day cycle.
So if you are using the calculator with the day the baby was born that could skew the results, especially if your baby was born earlier or later (which can happen during any pregnancy).
In order to calculate the estimated conception date, the calculator will use the last menstrual period date, and then add 12-16 days to it.
With the estimated delivery date, it will count back 38 weeks to give an approximate date of conception.
The conception calculator is great for mothers or expecting mothers who are interested in finding out when their baby was conceived (you know, either that trip to the Islands or when the power was out).
Now there are other calculators that we offer, such as ovulation calculators, implantation calculator, due date calculators, and sexual intercourse timing calculators.
These are useful for women interested in their fertility and determining when they have the best chance of becoming pregnant or when their next menstrual cycle will happen.
Facts about Conception
Women who experience regular period cycles typically conceive about 11-21 days after the first day of their last menstrual period.
Determining the exact date of conception is difficult and so your conception date is mostly an estimate based on your period cycle.
There are, however, special cases, such as women who are artificially inseminated or use in vitro fertilization, know the exact date of their conception.
Surprisingly, there are a lot of people who don’t actually know that you cannot conceive any time during the month.
According to one survey, more than 50% of respondents to a survey thought that this was the case, that no matter when you had intercourse you could get pregnant.
This causes many people to actually think they are infertile, when in fact they don’t know that there is a specific fertile period to go by.
Calculating based on your Estimated Due Date
Typically, your estimated due date is about 40 weeks from the first of your last menstrual period, but this is just an estimate.
While we consider pregnancy to be 280 days (40 weeks), it’s really only about 38 because the two weeks before/during ovulation you aren’t pregnant. You likely did not conceive till two weeks after the start of your cycle. (Embryonic growth lags two weeks on your pregnancy).
Figuring out your conception date based on your EDD is also an estimation. And while you are given an EDD, a lot of babies are not actually born on that day.
If you are trying to calculate the approximate conception date based on your due date you would take your due date and subtract 266 days. This would bring you back to your rough conception date.
Calculating Based on your LMP
With regards to the Last Menstrual Period or the LMP, it is pretty straightforward to calculate. But this can be confusing for women who have irregular periods.
Basically, the first day of your menstrual cycle is also the first day of your LMP. This works well if you have a regular cycle and those who are using natural family planning will be very astute to when their periods will come, when their body is ovulating, and when to expect PMS, etc.
However, most of the time, the first day of the LMP is usually what’s needed and nothing more with regards to that period.
Girls are in their fertile window to conceive a baby when they are ovulating. During the ovulation, girls release an egg from one of their ovaries. The newly released egg can travel down to the fallopian tube, male sperm can also swim up into the fallopian tubes, and it results in the fertilization.
Ovulation happens typically about two weeks following your menstrual period and continues for a couple of days. However, not all girls have exactly the same duration of cycles.
Many women’s menstrual cycles are very irregular. Others have ovulation intervals closer to or farther away from their menstrual period. That’s why calculating conception by focusing only on your body cycles can be hard.
Calculating Based on Ovulation Dates/Fertile Period
You can also get to know your ovulation date by using the Ovulation Calculator. As mentioned above, the exact date will depend on having a regular period which is on average 28 days (from the first day of one period to the first day of your next period).
Some women can tell when they ovulate, and this gives them a very good indicator as to when they conceived as well.
Women who are in turn with their bodies can notice the subtle changes such as changes in the cervical mucus, heightened sense of smell, breast tenderness, pelvic or lower abdominal pain (some can even tell which side they ovulated from), light spotting, and a heightened sex drive (your body wants you to get pregnant).
Knowing when you ovulate can help you get pregnant. Fertilization occurs when the sperm meets and finds its way into the egg which happens within 24 hours after ovulation.
And remember, sperm can survive inside the female for five to seven days, so you could conceive, even if you didn’t have intercourse on that day.
The basal temperature method is another way to figure out the days past ovulation, otherwise known as your luteal phase, which are the days between ovulation and the day before your next period.
Calculating Based on your Ultrasound
Another way to find your estimated date of conception is through an ultrasound. Ultrasounds are typically conducted between 8 and 20 weeks of pregnancy and are used to determine the gestational age of the pregnancy.
What Can Affect Conception Dates
There are many factors that can affect when you can conceive. Sperm only last from three to five days, and ultimately it is important to get that sperm into the woman during ovulation.
However, there are things that affect ovulation time-frames. Even when you generally have a regular cycle, there are situations in life that can make that cycle go awry.
There are also things that can affect conception even if you are having intercourse during your ovulation period.
Your body also has to be healthy, and if it isn’t then you might not actually conceive. When there is a lack of nutrients in the body such as zinc, vitamin D, vitamin B6, it could affect the reproductive hormones, which naturally can affect conception.
Another big factor when it comes to conception would be stress. When stress hormones are high, there is a 29 percent lower chance of getting pregnant.
So that stressful job, life, arguments, and illness can all wreak havoc on the body and conception. Take a break from the stressors in life and find a way to create a Zen place in order to help you conceive.
Medications are another huge one. Antibiotics especially, as well as other medications, can cause a delay in your ovulation and your cycle, which means that if your cycle has been altered, you won’t be able to accurately estimate when you conceived.
Additionally, eggs typically take from 12 to 24 hours to shed, meaning that the conception date may be off by one day.
Is the conception calculator practical?
The practicality of using this calculator varies from woman to woman. Although it can’t say that a baby was conceived on that specific date with 100% certainty, it can provide a solid prediction.
In addition, in situations where a woman had different partners at a given time and would like to know the father of her baby, using a conception calculator can give her a clue. However, a paternity test will be much more reliable in this case, especially if the woman wasn’t ovulating during those times.
Still, the only way to accurately know the exact conception date is when pregnancy is conceived through treatments such as artificial insemination and in vitro fertilization; otherwise, the conception calculator can only give you an estimated idea of the time your baby was conceived.
That is the reason a pregnancy affirmation ultrasound would be the very best method to understand just how far along your pregnancy is.
Pregnancy ultrasounds look right at the crown rump length (CRL), which is the length of fetus from head to buttocks, to determine its age. This way is a lot more precise than date-based calculation.
Frequently Asked Questions About Conception Dates and Conception Calculators
Is the date given accurate?
It’s an estimate and gives a range based on your fertile period. The only way to know for a fact when you conceived is if you only had intercourse once between your cycles. The only way to know for sure is through ultrasound scan done after 8 weeks of pregnancy.
Can the conception date determine the father of my child?
It depends on when you were fertile and when you had intercourse. If you had intercourse with multiple partners during that time-frame, it could be either of them and the only way to accurately know is by a DNA test.
Why would I want to use a conception calculator?
As said in the above question, you might want to have a range as to when you actually conceived, especially if you were with multiple partners. You also might want to have an idea as to where you conceived to tell your children later on and embarrass them.
Do you have any other question about your period, ovulation, pregnancy or other related topics? Check out our Frequently Asked Questions page.
References
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1. Sozou, P. D., & Hartshorne, G. M. (2012). Time to pregnancy: a computational method for using the duration of non-conception for predicting conception. PloS one, 7(10), e46544.
2. Gnoth, C., Godehardt, D., Godehardt, E., Frank‐Herrmann, P., & Freundl, G. (2003). Time to pregnancy: results of the German prospective study and impact on the management of infertility. Human Reproduction, 18(9), 1959-1966.
3. Abell, A., Juul, S., & Bonde, J. P. E. (2000). Time to pregnancy among female greenhouse workers. Scandinavian journal of work, environment & health, 131-136.
4. Mathiesen, J. M., Secher, A. L., Ringholm, L., Nørgaard, K., Hommel, E., Andersen, H. U., … & Mathiesen, E. R. (2014). Changes in basal rates and bolus calculator settings in insulin pumps during pregnancy in women with type 1 diabetes. The Journal of Maternal-Fetal & Neonatal Medicine, 27(7), 724-728.
5. Diedrich, J., Cortez, S., Benzoni, N., & Madden, T. (2015). Pregnancy calculator and cost-effectiveness analysis of three methods of postcoital contraception. Contraception, 92(4), 388.
6. Thomas, G. M., Lupton, D., & Pedersen, S. (2018). ‘The appy for a happy pappy’: expectant fatherhood and pregnancy apps. Journal of Gender Studies, 27(7), 759-770.
Hi im wondering who the father is because the 1st day of my menstrual period was the 9th of December 2020 and it ended the 16. I had sexual intercourse with someone else the 17th and then I had sexual intercourse with my boyfriend the 18th throughout til January 4. Which one is most likely to be the father. Because don’t you ovulate 10-12 days before your next period starts
Hello Rosa!
Given your last menstruation to be Dec. 9-16, it is most likely that your boyfriend is the father. The sexual intercourse you had on the 17th is safe. However, the ones you had on the 18th onwards belongs on your ovulation window which is Dec. 19-23. I hope this helps!
Hi,
My period started on Aug.22,2020 and I had sex with partner A on the 1st of September. I also had sex with partner B on September 4. Who could be the father? Help.
Hello Grace!
The sexual intercourse on both guys are done within your fertile window which is on Sept. 1-5. Have you seen a doctor? How long are you on your pregnancy? If you have the date, we can count the days and check who the father is. I hope this helps!
So I had unprotected sex on 0ct 5 with Guy A, then again on Oct 9 with Guy B!!! I got my period on Oct 10 and now I’m about 9 weeks period!!! Could I have got pregnant on Oct 5 with guy A!!!
Hello Indrea!
If you had your period after you had sex with both guys, then no conception occurred. Have you visited a doctor regarding this matter?
Hi so as of today October 30, I’m currently 12 weeks and 2 days pregnant. On July 30, I had sex with a guy and then in August 7 I had my period well. I think it lasted about 3 days and a half. After that I started seeing my ex again and was having sex with him all August. Now I don’t know who the father could be. Can anyone help me and help me figure out my conception date
Hello Nat! The unprotected sex on July 30 didn’t conceive a baby because you had your period on the 7th. This means you had sex during week you were not ovulating. Based on your sexual activity and your last menstrual period, your possible conception date is around August 16-31.
I had sex with a partner on 28th December, 2015. Again she went to have another sex with partner B in the 3rd January, 2016. I want to know who is likely to be the father of the kid. He was born on 14th September, 2016.
Hello Victor!
If the child was born on the 14th of September 2016, the child’s probable conception date is December 28, 2015.
Hello there, I had unprotected sex on the 12th of March 2020 with guy A and my period was late for 3 days. I was supposed to get my periods on the 26th of March but they came on the 29th of March 2020 and lasted for 4days. Then had sex with guy B on the 6th of April 2020 and missed my period that month. On the 23rd of May, I found out I was pregnant then went for an ultrasound on the 15th of June my EDD was 28 December 2020. Who’s the father?
Hello Mimmy! First, congratulations and stay safe on your coming delivery. Based on the information you have provided, guy B is the father. Based on your EDD, the possible conception date is around April 3-April 13. And since you only had sex with guy B after your menstruation on March, he is then the father.
I had sex July 2nd with one guy & July 19th with the other. Currently (todays date is October 17 2020) my doctor says I’m 15 weeks & 2 days.
So when I googled 15 weeks ago it said July 4 subtract 2 days & you get July 2nd so is guy #1 the daddy?
Hello there! Based on your ultrasound, yes you are right that it is guy #1.
Hello I had sex on June 21,2020 with my bf. My period usually comes at the end of the month but I only bled for 2-3days which is irregular. Me and my bf broke up then I had sex with someone else on July 5th. I am due March 30th 2021. Who could be the father?
Hello Sarah! Congratulations on your new bundle of joy. To answer your question on who the father could be, it is the guy you had sex after your June period. Since your due date is March 30, 2020, the possible conception dates range from July 4 to July 14. I hope this helps you out.
i had sex with this guy i be talking to for a while on august 8th then i had my period. But i don’t remember when but i know it was in the end of August then we had sex September 19th. I got my period on the 23rd but my stomach been cramping & my back been hurting & certain smells like taco meat smells horrible to me & my back kind of sorta hurt , & i been tired , i could sleep all day
Hello! You can still have stomach cramps and back pain during your menstruation. Pregnancy and menstruation almost have the same signs aside from a positive pregnancy test.
I was supposed to see my period on the 4th of September… I conceived on the 10th of August but nothing shows and no signs of pregnancy nor period pains nothing… What does that mean?
Hi! So aside for the delayed period, there is no other pregnancy symptoms right? Have your tested and confirmed if you are indeed pregnant? If so, there should be nothing to be worried about. Pregnancy signs are different in one person, and different to another. Some of the signs even come later. Visit your doctor to learn more of your pregnancy and best of luck!
Hi. I need help. Can anyone help me I am new to this. I had unprotected sex with GUY A on December 22nd and had my regular period on December 24 – 28. Then had sex with GUY B on December 30 till January 12.
My first scan in February 7 said I was 6weeks who is the father
Hi Grace. Based on your timeline, the father is GUY B and around Jan.3-18 is your conception date. It is also possible to have conceived the day you had sex with GUY B if we base on your scan. Congratulations!
I had sexual intercourse with two partners i had sex with patner A on the 1st of February 2019 then partner B on the 11 February my child was born on 31 October 2019 help plz to find out who is the farther of my child
Hi, my last period was November 8, 2019. I’m due august 13, 2020. I had sexual intercourse Nov 17&18, 2019 by the same guy. Then, not to sound wrong but I had sex again nov 25,2019, different guy. Who is most likely the father? Please help me.
Hello. I am 28 weeks pregnant now. I have had a lot of anxiety about my situation for months. On December 21, 2019 around 4am I had sex one time with partner A. He had trouble keeping an erection and we used condoms. But we did have unprotected sex for about a minute. But after that minute he couldn’t hold the erection again, so we just stopped having sex. He never ejaculated or came close to ejaculating.
On the night of December 23, I had sex with my main partner (B). It was completely unprotected. And my partner ejaculated but not inside. I thought he had “pulled out” in time. I have went about my pregnancy with confidence that the father is partner B due to the circumstances. But I am just needing to hear it from someone else that it is possible to get pregnant on December 23 with an expected period the 3rd or 4th of January 2020. Partner B has gotten me pregnant twice before without ever ejaculating inside, so I’m thinking he may have a pre-erection problem.
My due date is September 14, 2020.
I have a condition called vaginismus which makes penetration and sex kind of difficult. I attempted to have sex with Guy #1 on May 20. He put on a condom and attempted to put his penis in me and only got about halfway in before I told him he had to stop because I was in pain. On the night of May 24 and morning of May 25th, I had successful sex with guy #2 about three times, which also happened to be my ovulation day. When I went to the doctor, I found out I got pregnant on May 27. My period was from May 13-May 18 and my due date is February 27, 2021. I just wanna confirm that guy #2 is the dad.
Actually I don’t remember the accurate due date, but I know it’s toward the end of February 2021.