DPI vs PPI

Strictly speaking, PPI (pixels per inch) belongs to images and screens, and DPI (dots per inch) belongs to printers. In practice almost everyone, including Photoshop menus and print shops, says DPI for both. Here is what that means for your files.

PPI: pixels per inch

PPI describes how many image pixels fit in one inch. It is the number saved inside your JPG or PNG, and the one you set when you “change DPI” in any app. A 2400 × 3000 pixel image at 300 PPI prints at 8 × 10 inches.

DPI: dots per inch

DPI describes the printer itself: how many tiny dots of ink it can place per inch. An inkjet printer rated at 1200 or 4800 DPI uses several ink dots, in different colors, to build each pixel of your image. That is why a printer's DPI is always much higher than the image's PPI.

So which one do I need?

When a print shop asks for “300 DPI”, they mean an image file with enough pixels to print at 300 pixels per inch at the final size. You do not need to worry about your printer's dot resolution; that is their job.

To check your file, use the DPI checker. To set it, use the 300 DPI converter. And to know if you have enough pixels, look up your size in the print size table.