Bill, a 2x is supposed to measure 1-1/2", a 4x is supposed to measure 3-1/2" and a 6x is supposed to measure 5-1/2". Non-treated lumber hits these dimensions fairly well normally but treated does seem to vary a little more. Remember, too that wood expands and contracts with changes in humidity and by different amounts depending on the orientation of the grain. Normally, you would expect to see a 4% change across the widest dimension. The percentage for change in length is smaller but it is over a longer span. If you really want accurate dimensions, you have to measure every piece and even then you can see variation from end to end.