Square peg/round hole (DPI vs PPI)

Both DPI (dots per inch) and PPI (pixels per inch) refer to a graphic’s resolution. What is the difference?

PPI

The term “pixels per inch” is used when speaking of graphics in the computer. It refers to the number of pixels used to reproduce an image.

DPI

The term “dots per inch” is used when speaking of printers and paper/film output. It refers to the number of dots used to reproduce an image (not to be mistaken with LPI or “lines per inch”).

What’s the difference?

Pixels are square and dots are obviously round. A computer’s monitor renders images, text, etc. as a series of square boxes of varying lightness and hue while a print output device (such as a printer or imagesetter) uses a series of round dots to reproduce the image.

LPI

The term “lines per inch” is used when speaking of printers and paper/film output. It refers to the number of rows of dots used to reproduce an image. The greater the number of lines per inch, the finer the detail able to be reproduced. However, The ideal LPI rate is dependent upon several factors including the type of paper, the type of press and for what the printed piece will ultimately be used. Generally, newsprint is produced at 85 LPI, uncoated paper projects at 85–120 LPI and coated art prints/magazines at 150-200 LPI.