You should only give consideration to inches if you will output to a printer or other offline format, as others have said. If this consoderation must be made, it is the FIRST consideration to make. If you spend all your time and work on a 300x300 pixel image, and you want to print to an 8 inch square, you're screwed. Interpolate all you want, the printed output will not look good. In general, if you're planning to print on a home-quality color inkjet printer, 150dpi is sufficient... so do the math and figure out how many pixels you need for your desired output size. If you'll print on a laser or dye-sub printer, you'll want 300 - 600 dpi output, or, two to four times both the horizontal and vertical pixel resolution of the above (four to eight times the area resolution). I believe the Photoshop manual devotes several pages to resolution and dpi. -sk