Is My Conception Date Accurate From Date Of Conception How Many Days Is The Due Date Accurate?

From date of conception how many days is the due date accurate? - is my conception date accurate

Ultrasound examination at my 11wks 4 days, says my due date is 23 July and many days is of the opinion that accurate.is is like a day or two, or give one or two weeks from conception date. calculated, I hope its not too confusing, I