First Day of Last Menstrual Period: October 23, 2011
Probable Date of Ovulation: November 6, 2011
Possible Dates of Conception: November 2 to November 10, 2011
Due Date: July 29, 2012 (40 weeks)
my lmp was october 25 , 2011 and i am due July 31, 2012 ... you would have had to had a period in november to have a due date of august 13.