ppiDPI

ppiDPI is a colloquial term sometimes used in digital imaging to describe the relationship between pixels per inch (PPI) in a digital image and dots per inch (DPI) produced by a printer. It is not an official unit or standard; rather, it reflects how changes in one metric affect the other in print workflows.

Because PPI and DPI measure different things, they are not directly interchangeable. PPI describes how many image pixels appear in each inch on a display or within a raster image, while DPI describes how many printer dots are placed in an inch. In practice, the term ppiDPI is used to discuss the expected print quality when an image of a given PPI is printed at a given DPI, but it does not encode a fixed ratio.

To print with sharp detail, the image's PPI should be set considering the target print size and the printer's DPI capabilities. Example: an image at 300 PPI printed at 600 DPI can be rendered with multiple printer droplets per image pixel, potentially yielding smoother edges; however, actual results depend on printer technology and dithering.

Calculating print dimensions: print width (inches) = pixel width divided by PPI. If you want a 6-inch-wide photo at 300 PPI, you need 1800 pixels across. For a given display or publication standard, adjusting PPI or DPI changes the required file size and perceived quality.

There is no formal standard for ppiDPI; professionals instead manage PPI and DPI separately in image editors and printer drivers, and rely on viewing distance and output device specifications to judge quality.

See also: PPI, DPI, image resolution, print quality.