CPI and DPI are two different measurements for the same thing: how much mouse movement is needed to move the cursor from one side of the screen to the other. In short, CPI is a measurement from the center of the screen to the center of the cursor. DPI is a measurement from the center of the screen to the center of the cursor, and its expressed as dots per inch (DPI). CPI and DPI are sometimes used interchangeably, but they are not the same thing.