I went to the Dr. on Monday and they said I was about 18wks and gave me a due date of July 5th. I believe he went by using my LMP. Then I got an ultrasound and the tech. gave me a due date of July 8th. She also said to subtract 2wks from the 18wks the Dr. gave me which I guess would make me 16wks? I'm confused?! The sonographer also said I conceived around the middle of Oct. I had sex Oct. 4th and Oct. 11th. Do you think these dates add up correctly. Is the ultrasound more reliable?

July 5th and July 8 aren't that far apart. I mean, I would not worry about 3 days, usually a due date can be 2 weeks give or take. It is all just an educated guess.

Prediction dates are estimates, guesses, they are never exact. So either date could be correct for conception, And in the end the baby comes when it wants to anyway, so it really does not matter which conception date ( unless it was not the same man of course)

Oh it's the same guy! I guess I just wanted to know how accurate are ultrasounds with giving the due date and age of the baby?

Put a bunch of dates on a dart board and throw a dart about that close.

They use educated guess, by looking at the size of the infant in comparison wth normal and standard infants at certain sizes. But all children develop slightly different speeds,

Might be best to just think of yourself as due "around the beginning of July". Sometimes too much emphasis is placed on exact due dates.