How far along am I in my pregnancy?

You can calculate how far along you are using our Pregnancy Calculator.

Dating a pregnancy can cause confusion, because it can be done in either of two different ways. Pregnancy can be dated from the first day of the last menstrual period or it can be dated from the day of ovulation.

In the United States, pregnancy is dated from the first day of the last menstrual period. This is a holdover from a time when much less was understood about conception. No one understood that ovulation was required for conception or when ovulation occurred. However, most women know when their last menstrual period was and it was known that the average pregnancy lasts 280 days (40 weeks) from the first day of the last menstrual period. According to this system, conception doesn’t actually occur until 2 weeks of pregnancy. Obviously, you aren’t pregnant until conception occurs. This is just an artifact of the old system.

In many other places, the new knowledge has been incorporated into a dating system that starts with conception. In that system, pregnancy starts on the day of ovulation (usually the day of conception) and lasts for 266 days (38 weeks).

In both systems, the due date is exactly the same. It only makes a difference in calculating how far along you are during a pregnancy. For example, in the American system, the first trimester ends at approximately week 12, whereas in the other system, the first trimester ends at approximately week 10. The following table illustrates the differences:

Similarly, if you are trying to calculate backward to figure out when you conceived, you need to know what system your doctor used when calculating your dates. In the American system, if you are 7 weeks pregnant, you conceived only 5 weeks ago.