Printer specifications are real and accurate and meaningful, but are not to be confused with image resolution. Printer ink dots and image pixels are simply very different things, and one color image pixel requires many printer ink dots. This is why we need a 1200 dpi printer (ink dots) to print an image at 250 dpi (pixels).
Q: What are the standard postcard sizes you offer? A: For flat standard postcards, available sizes are as follows: 4 x 6, 4.25 x 6, 5 x 7, 5.5 x 8.5, 6 x 9, and 6 x 11. Folded postcards have 2 kinds: half-folds and tri-folds.
Each postcard claimed at a card price must be rectangular and must meet the following dimensions: 1  Not less than 3-1/2 inches high or 5-1/2 inches long or 0.007 inch thick. 2  Not more than 4-1/4 inches high or 6 inches long or 0.016 inch thick.