Photoshop :: Ruler Scale Not Proportional On Screen?

The ruler scale isn't proportional on my screen for the height and width. The canvas size is only 3 x 5, so I don't think it's because the file is too big. The file looks great on screen, but when I print it out the image proportions I see on the screen aren't the same as the print out. When I look at the ruler, an inch is much longer on the height than it is on the width. I'm viewing in Print Mode, but have also tried fit on screen and actual pixels (which makes it too big to see, of course). I tried resetting all tools, but no luck.