Pregnancy Calculator By Due Date

Pregnancy Calendar Calculator

Use our due date calculator by conception date to estimate when your baby is due. Just click on the first field to use the calendar and then click the calculate button.

Click on the First Day box for a popup calendar:

First Day Of Your Last Menstrual Period:
How Long Is Your Menstrual Cycle?
(22 to 45 days) (defaults to 28 days)
Estimated Date Of Conception:
Estimated Due Date:
Estimated Fetal Age:


How Many Weeks Pregnant Am I? How Is It Calculated?

A “normal” pregnancy lasts 40 weeks or 280 days. The estimated due date is based on the length of your menstrual cycle and the 1st day of your last menstrual period (LMP).

If you have a regular 28 day cycle, your due date will be calculated as follows:  Date of 1st day of your LMP + 280 days.

If you have a longer or shorter cycle the calculation is adjusted by adding or subtracting the required number of days. For example, if your cycle is 31 days then your estimated due date will be: Date of 1st day of LMP + (31-28=3) + 280. So 3 extra days are added. If your cycle is shorter, you will have ovulated earlier and therefore you have to subtract accordingly. For example if your cycle is 25 days, your due date will be calculated as follows: Date of 1st day of LMP + (25 – 28 = -3) + 280. Therefore it will be 3 days shorter.

Use the calculator above – it is much easier than trying to do the maths!

Keep in mind that this is an estimated due date and only about 5% of women actually deliver on that date. In a normal healthy pregnancy, it can be any time after 37 weeks.

What Do You Mean By “Fetal Age”?

Fetal age is the actual age of the fetus based on conception and gestational age is the age of the pregnancy based on your LMP.

As you conceived after your LMP, fetal age will always be less than the gestational age by about 2 weeks.

For information about your week by week fetal development, check out Fetal Development Week By Week and select your relevant week as calculated in “Estimated Fetal Age” above.