Here is a video explaining the difference between dpi and ppi.
Dots Per Inch (DPI) is a measure of spatial printing or video dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (~2.54 cm). DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain, which is the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media. For a more detailed look visit this page.
Pixels Per Inch (PPI) is a measurement of the pixel density (also known as resolution) of devices in various contexts. For the most part this refers to displays, scanners, and digital camera image sensors. PPI is defined as the horizontal or vertical density (for square pixels) as those are the same but the density on along the diagonal is lower. Square pixels are the norm (otherwise those densities would be different). For a more detailed look visit this page.
Bennett H writes in via email:
I found your page searching for pages that purport to "clear up the confusion" around DPI vs. PPI.
I think part of the confusion over "PPI" is that there are in fact two different definitions in widespread use:
- the physical pixels per inch on a monitor screen (which of course
can't be changed)
- the metadata PPI in an image file, which is ignored by the monitor, but tells the *printer* (not the monitor) how many pixels to print per inch of space on the paper
When you say "Pixels Per Inch (PPI) is a measurement of the pixel density (also known as resolution) of devices in various contexts", you're talking about the first definition. But it might be useful to tell readers that there are two definitions and you're just talking about the first one.