Last updated on April 27th, 2021

The moment couples learn of their pregnancy, they are eager to find out when their baby will make its grand debut. But, some are equally excited to determine the date when their baby was conceived. 

You’re one of them, and you’re not very keen on troubling your doctor for it. Then, is it possible to calculate the conception date manually? Yes, it is.

By taking into account a few important dates and after a series of mathematical calculations, you can determine the conception date. However, one must remember that calculating the conception date whether you do it manually or using an online calculator is only an estimate figure and not accurate. 

Nevertheless, calculate the conception date and learn when your baby was conceived. 

Calculating the Conception Date Manually

In order to calculate the conception date, you will need to know the date of the Last Menstrual period and the length of your menstrual cycle. There are two methods to calculate this date.

The Regular Method

According to this method, you will require to chart your ovulation date.

The normal menstrual cycle lasts for 28 days. You count from the first day of one period to the first day of the other period. The menstrual cycle is divided into two stages – the follicular stage and the luteal phase. The two stages roughly span 14 days each. It may be more or less for some. 

Conception Date


Ovulation is the point in the menstrual cycle when a woman is most fertile. Ovulation occurs in the middle of the menstrual cycle. Thus, for a regular menstrual cycle lasting 28 days, ovulation occurs on the 14th day. However, if you have a longer cycle, ovulation occurs later. 

Subtract 14 from the length of your menstrual cycle to find out the tentative days of ovulation. For example, if the length of your menstrual cycle is 30 days subtract 14 from it. The remainder is 16. You likely ovulated on the 15th or 16th day. Conception usually occurs 24 hours of ovulation. Thus conception may have taken place on the same day or the following day.

Many women mistake the day they make love to be the day of conception. However, it is not so. Conception depends upon the time when ovulation occurs. The male sperm can live in the female system for up to five days. Thus, if you had intercourse five days before the date of ovulation, you can still get pregnant.

The Reverse Method

This method calculates the conception date based on the due date. Doctors count the average length of pregnancy as 40 weeks or 280 days. He counts from the first day of the last menstrual period. This implies that the counting includes even the two weeks before you may have conceived. 

Thus, when you know the due date, subtract 266 days from the due date, i.e. 280 days backwards. You will know the date of ovulation. The date of ovulation or the day after that could be your conception date. 

Online Conception Calculators

If you’re not very good at numbers, you can simplify the process using an online conception calculator. Enter your due date in the given slot, and it will calculate the possible dates when you got pregnant.

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