May sound dumb

[WildRose32]

Ok may sound dumb but I had my last baby 8 yrs ago...when they measure the  baby they ccan figure out how far I am right?

[jamie4321]

yes the u/s can tell you how far you are good luck to you

[AnnieBrooke]

The short answer is that with an ultrasound, they can figure out a date to within about 2 weeks.  

If you have an early ultrasound, i.e., one at around 7 to 8 weeks after the first day of your last period, the dating can be more exact.  But a later ultrasound will not be able to pinpoint things any closer than a week or two.  

Please remember that if your question is "when did I conceive," do not ask the doctor "how far along".  A doctor will give you a count based on the first day of your last period, not on the conception day, when asked that second question.  He or she will not immediately assume you are asking about the possible day of conception unless you say so.

If you just want to know what your due date is, the doctor will use the first day of your last period and that is fine.  It all calibrates.