Pixels per inch (PPI) or pixel density is a measurement of the resolution of devices in various contexts; typically computer displays, image scanners, and digital camera image sensors.
PPI can also describe the resolution, in pixels, of an image to be printed within a specified space. Note, the unit is not square inches. For instance, a 100×100 pixel image that is printed in a 1-inch square has a resolution of 100 pixels per inch (PPI). Used in this way, the measurement is meaningful when printing an image. Good quality photographs usually require 300 pixels per inch when printed.
