dotperinch

Dotperinch is a nonstandard term used in some digital imaging contexts to describe the density of output elements—dots or samples—per inch. It is encountered in relatively informal discussions, marketing literature, and certain workflows as a shorthand for image resolution. However, it is not recognized as a formal unit by major standards bodies, and its precise meaning can vary between sources.

In professional settings, the terms DPI (dots per inch) and PPI (pixels per inch) carry explicit definitions. DPI refers to the printer’s capability to lay down individual color or gray-scale dots per inch, which depends on the device's engine, ink, and halftoning. PPI denotes the sampling resolution of a digital image or display, i.e., how many picture elements exist per inch. The two are related but not interchangeable: a high PPI image displayed on a low-DPI device will still appear sharp; a high-DPI printer can render many dots per inch even if the source image has modest PPI.

As a result, dotperinch should be interpreted with caution. When preparing imagery for print, designers typically specify target DPI to ensure sufficient dot density after halftoning, while for screens the display resolution is determined by PPI and viewing distance. Calibration and profiling can align device capabilities with output expectations.

See also: DPI, PPI, resolution.