<<How do I do this? What width is standard printout width.>>
Not sure I undetstand the question. Within an Access report, you can size the report any dimension you want basically.
Beyond that, there are standard paper sizes, but it varies by country. Here in the US, a standard page is 8.5" by 11.0.
Margin spacing is up to you (which would reduce the size of your image). Again the standard here is 1" margins.
The last factor would be the printer iteself; most cannot print to the edge of the paper. So even if you have 8.5 x 11.0 paper, you may not be able to use all of that.
Hopefully I've hit enough points to answer your question. If not, bounce back with a little more detail on what it is your attempting to do exactly.
JimD.