Measurement question?

 From:  mash
4642.1 
Hi, if I bring in a IGES file and set the unit system to Centimeters how accurate would the measurements be?
I'm assuming because it's an IGES file used for manufacturing it would be accurate.
I just don't know if IGES file stays the same scale in differnt software packages.
Is there any way to measure objects other than counting grid squares?
thanks