Based on 28 day cycle.
First Day of Last Menstrual Period:October 11, 2008
Probable Date of Ovulation: October 25, 2008
Possible Dates of Conception: October 21 to October 29, 2008
Due Date: July 18, 2009 (40 weeks)
Depends on the length of your cycle.
Babycenter. com has an ovulation calculator that you can put all your info in to find you most likely conception date.