Conception Calculator

How to Know When You Conceived

In general, women can only conceive when they are ovulating – that is, when their ovaries release a new egg into their fallopian tubes for fertilization. Ovulation usually occurs about two weeks after your menstrual period and lasts for two or three days.

However, not all women have the same cycles of menstruation and ovulation. Some women’s menstrual cycles are irregular. Others have ovulation periods closer to or further from their menstrual period. Some women simply aren’t sure when their last period was. In other words, calculating conception based just on your body cycles can be difficult.

You can also simply try to determine the last time you had sexual intercourse, but this method isn’t totally accurate either. Conception is a process and takes time, and a man’s sperm can actually stay alive inside your body for up to a week after sex. All of these factors can make it hard to know when exactly you conceived.

This is why a pregnancy confirmation ultrasound is the best way to know how far along your pregnancy is and to determine when you conceived. Pregnancy ultrasounds look directly at the development of your growing baby to determine its age and when you likely conceived. This method is much more accurate than date-based calculation.