Calculating Due Date, Conception Date
& Fetal Age

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calculating due date
Calculating due date is a fun thing to do both when you are pregnant and trying to conceive (or even just secretly dreaming about it).

Use the pregnancy due date calculator below to estimate your due date as well as conception date and fetal age. Just remember that the estimated due date is just that - an estimation.

Even if we typically say that a pregnancy is 40 weeks long on average, calculated from the first day of your last menstruation, a baby is actually considered full term already at 37 completed weeks, i.e. in the beginning of the 38th week of pregnancy.

Also, a study carried out already back in the beginning of the 1990s, indicated that most women do not give birth at 40 weeks, but later. According to the study, there were marked differences between Caucasian women and afro-american women and between first pregnancy and second. You can read more about this in our article about being 40 weeks pregnant.

For calculating your due date, conception date and the age of your fetus, use our simple due date calculator below.

Due Date Calculator

Here is how to fill out the figures correctly:

Last Menstrual Period: Simply the first day of your last period

Average Length of Cycles: What is the average length of your menstrual cycle from day 1 in one in 1 cycle to the very last day before day one of the next cycle? If the cycle length vary, try to use the most common length or an average.

Average Luteal Phase Length: This is the length from the day of ovulation to the 1st day of menstruation. This period of often around 14 days. If you haven't been trying to conceive for a while and haven't tracked your ovulation, you may have no clue how long the luteal phase is. In such case, simple add in 14 days.

Now you are ready to find out when your baby is due!

Last Menstrual Period: 
(MM/DD/YYYY format)
Average Length of Cycles: (22 to 45)
(defaults to 28)
Average Luteal Phase Length: (9 to 16)
(defaults to 14)

Estimated Conception:
Estimated Due Date:
Estimated Fetal Age:

Interpreting the results:

If you filled out everything correctly, you should have a due date now. You also get a conception date, which is calculated as the day before the start of your lutheal phase, i.e. the day of your ovulation. (To learn about ovulation symptoms, click here.

You also get the age of your fetus. This fetal age is not the same as the pregnancy weeks referred to in almost all pregnancy calenders and articles (including the articles on this site). The reason is that pregnancy weeks (or gestational weeks, as they are called) are calculated from the 1st day of your last period at that time, you obviously did not have a fetus in your womb. So fetal age is 2 weeks less than the pregnancy week you are in. For example, when calculating your due date above, and the age of the fetus is 6 weeks according to the calculator; you are already 8 weeks pregnant. If this sounds confusing, we have added information about fetal age in every pregnancy week article here at Easy Baby Life, to help you out.

Now when you know your estimated due date and fetal age, you can read about your baby's development and what is happeing with your own body in every week of your pregnancy, by going to the different pregnancy weeks in the left column. Or you can start by getting an overview in both pictures, videos and words in our week by week pregnancy calender here.

Have fun!

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By Paula Dennholt, Copyright © 2006-2013 EasyBabyLife.Com. Please review our disclaimer before using this site.

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