The pixels per inch of a display is what is called pixel density or PPI. It is a measure of how many pixels you would count if you were to count the pixels, horizontally or vertically, that appear in one inch of your display.
PPI is imaginary! PPI vs DPI vs resolution
Now you know your display’s PPI… but what good does it do you? If you were just curious, you’re done! However, as we mentioned in the introduction above, knowing the PPI of a device or display is usually the first of two steps toward something much more practical.
If all pixels were the same size, the pixels in an inch would be a known number, such as centimeters in an inch (2.54) or inches in a foot (12).
However, pixels are different sizes on different displays. For example, the answer is 58.74 pixels per inch on a 75-inch 4K TV, but 440.58 pixels per inch on a 5-inch Full HD smartphone screen.
