Demystifying the Jargon
DPI (Dots Per Inch) and PPI (Pixels Per Inch) are often used interchangeably, but they refer to different things. PPI refers to digital screens, while DPI refers to physical printers.If you're designing a website, physical size doesn't matter as much as absolute pixel dimensions (e.g., 1920x1080). But if you're printing a flyer, the density of those pixels—the DPI—is crucial.
Web Guidelines
For the web, focus on file size and pixel dimensions. A 1200x800 pixel image will look the same on a monitor whether it's tagged as 72 DPI or 300 DPI, because monitors display pixels, not inches.However, for high-density displays (like Apple's Retina screens), you often want to export images at 2x their display size to ensure they remain crisp.
Print Guidelines
When a commercial printer asks for 300 DPI, they mean that for every inch of physical paper, there must be 300 pixels of data. If you print a 1000x1000 pixel image at 300 DPI, it will print at roughly 3.3 x 3.3 inches.Before sending anything to print, always verify your document's resolution. You can't magically upscale a low-resolution web image to 300 DPI without making it blurry or pixelated.