My last period was in 6th sep ended in 10th sep.my doc said im 12 weeks and 3 days pregnant.can u tell me the exact day i conceived. ?

Nonsense : That's an estimate. He didn't give you the number of hours and minutes did he?? All tests have error bars and whatever tests he performed have them too, sometimes stated as plus or minus.

Not straightforward.: If your periods are irregular, you will use your LMP as the last objective milestone. Conception would be two or three weeks later if you are regular. An ultrasound will give you another point of reference. It will be an estimate. In the end the people who know the actual date of conception had in vitro fertilization. Best of luck to you.

Online calculator: Use a reverse due date calculator for free online and this will be easy for you to find out. Simply type in your due date and the conception date will be calculated for you. This is the exact way we would determine your conception date too.