Knowing the stage you are in can be confusing at the beginning of your pregnancy. We show you how to calculate weeks, months and trimesters in a simple way.


From the day your last menstrual period starts, 280 days are calculated to estimate your due date (LMP). However, weeks, months and trimesters are used to keep track of your pregnancy. 


How many weeks pregnant am I?

Weeks of pregnancy are calculated from the first day of the last menstrual period. From that moment it takes about 40 weeks until the moment of delivery, but it can be extended until the 42nd week. In reality, gestation lasts 38 weeks from the ovulation moment, which occurs about 14 days after the onset of menstruation. However, this is not exact, which is why the first date is the one being taken into account.

It is therefore advisable to record the days of your periods so that you can keep track of the weeks of your pregnancy correctly. Note that pregnancy is considered full term from 39 weeks to 40 weeks and 6 days.


How many months pregnant am I?

If we divide the 40 weeks by months of 30 days we get about 9.3 months. To avoid confusion and to know which month you are in, the most common method is to count 7 months of only 4 weeks and 2 months of 5 weeks. Specifically, the only two months that are considered longer than the rest are the third and sixth.


What trimester am I in?

Another indicator of the progress of the pregnancy is the trimesters. The first trimester includes the first 13 weeks. The second trimester goes from week 14 to week 27 and the third trimester lasts from week 28 to week 40, if not longer.


The following table will make your life easier to know exactly which week, month and trimester you are in: