A full term human pregnancy is to 259 - 280 days or 37-40 weeks.
This is calculated from the first day of your last period, so to be more accurate, if conception took place 14 days after the first day of your last period, you need to subtract 14 days from the 259-280 days.
However, the way the medical community gages it, a woman is considered 2 weeks pregnant the day she conceives because they chart the pregnancy from the first day of the last menstrual cycle.