Conception Calculator Based on Due Date

Many parents-to-be feel the need to know when their baby was conceived. With the help of a conception calculator based on due date, parents-to-be will be able to find out the conception date...
HerHaleness Staff
Last Updated: Mar 5, 2018
When a woman is confirmed to be pregnant, both the mother as well as the father are eager to know when will the baby be born. That is when the gynecologist makes use of the due date calculator, to predict the approximate arrival date of the new addition to the family. However, after a few weeks, the parents want to know when was their baby conceived. This is when the conception calculator based on due date comes in handy. It is also known as the reverse calculator, as the conception date is calculated based on the due date.
Conception Date Calculator
The two ways used to calculate the due date are using ultrasound, and identifying the last menstrual period (LMP) date. Similarly to calculate the conception date, there are two ways. They are:
  • Conception calculator based on due date
  • Conception calculator based on last menstrual period (LMP)
In this article we will concentrate on the first method.
Conception Calculator Based on Due Date
Under normal circumstances, women do not know the conception date, as it is very difficult to figure out the exact date. However, women who have undergone special procedures like in-vitro fertilization, or treatment for infertility often know the exact conception date.
When we use the pregnancy conception calculator, there are a couple of details which you will have to always remember. A woman is normally able to get pregnant for approximately 5 days each month. This is true because a sperm can stay alive for 3 to 5 days in the woman's reproductive track. Hence, even if the intercourse happens a couple of days before or after ovulation, the woman can get pregnant. Ovulation and conception occur on an average 14 days before the next menstrual cycle is due. However, this is true, if the menstrual cycle of the woman is normal and is of 28 days. If the menstrual cycle is longer, then the day of ovulation and therefore pregnancy, will be more than 14 days. The average length of the menstrual cycle ranges from 22 to 44 days. A 44 day menstrual cycle is, however, rare. When health care providers calculate the due date, they often consider the menstrual period cycle to be of 28 days. Therefore, chances are high that the baby may arrive a little later or earlier than the predicted due date.
The due date is calculated by adding 266 days to the date of ovulation and fertilization or ovulation. The alternative method is to add 38 weeks to the date of ovulation and fertilization. The duration of a normal pregnancy is anywhere between 38 to 42 weeks and the average term pregnancy is 40 weeks. Hence, to calculate the conception date based on due date, reverse calculations will have to be implemented.
Let us take an example to understand, how to calculate the conception date, using the menstrual cycle. For example, the last menstrual period was on 1 January.
Cycle Days Conception Date*
25 day Cycle 12 January
26 day Cycle 13 January
27 day Cycle 14 January
28 day Cycle 15 January
29 day Cycle 16 January
30 day Cycle 17 January
31 day Cycle 18 January
32 day Cycle 19 January
33 day Cycle 20 January
34 day Cycle 21 January
35 day Cycle 22 January
36 day Cycle 23 January
37 day Cycle 24 January
38 day Cycle 25 January
* - The values in the table are approximate values. You will have to calculate the conception depending on your ovulation cycle, which can either be longer or shorter than 28 days.
Conception Calculator Boy or Girl
It is very difficult and complicated to explain how to calculate if it is going to be a baby boy or a baby girl. The last menstrual period date and exact ovulatory cycle information is required to find it out. Among numbers of ways available, the Chinese lunar pregnancy calendar can help in predicting the gender of the child. This calendar makes use of the mother's age and the conception month to predict the sex of the baby.
The gender of a baby is determined by chromosomes. When a sperm carrying 'X' chromosome fertilizes an ovum, the baby conceived will be a girl. On the other hand, if a sperm carrying 'Y' chromosome fertilizes an ovum, it will be a baby boy. The date for screening is usually the 62nd day after the start of the last menstrual cycle.
Any conception calculator based on due date will be dependent on the due date. Therefore, the date will always be an approximation. It is best not to be unduly stressed about the conception date and rather concentrate on the growing fetus. Although science has gone way ahead, it has not been able to find exact answers to questions like the exact conception date.