Dots per inch is a measurement used for spatial printing and video dot density in which the number of dots that can be packed into a single inch of space is measured. While only related indirectly, the DPI value does tend to correlate with the resolution of a screen. DPI can be best seen when zooming in real close on something. The tiny dots are then visible to the naked eye. These tiny dots make up the images when looking at a printed picture or the screen.

DPI in Video Resolution

Because pixels are used when discussing resolution and not dots, there has been a growing trend of confusion amongst consumers. While it is correct to 320×240 pixel 3 inch monitor has 400 DPI, that is misleading because it assumes that there the resolution is considerable stronger than it actually is. As much as it is correct information–individual sub-pixels could be the dots–the customer is only going to see that it is 400 and believe that the product has a higher resolution than other, properly labeled products.

The more acceptable form of describing resolution is in pixels per inch. The more pixels that can be fit in an inch determines how high the resolution is. While sub-pixel colors of red, blue and green do make up the individual pixels, they should not be the number advertised to customers because it leads them to believe that they're getting a stronger resolution than they actually are.DPI - Dots Per Inch

DPI and Printing

When it comes to printing, it is typically acceptable to assume that the higher the DPI of a printer is, the better the quality of an image. The reason for this is because there are more dots filled into one inch and therefore, the image appears more crisp and clear. Different printers can offer different quality images, but this, in turn, results in a higher price depending on the printer.

  • Dot Matrix Printer: Has a low DPI  in the range of 60 to 90 DPI.
  • InkJet Printer: Has a medium DPI in the range of 300 to 600 DPI.
  • Laser Printer: Has a high DPI in the range of 600 to 1800 DPI.

To take an image that is from the monitor and then print it out and have it be as clear with the correct colors seen on the screen, the DPI has to be considerably higher than the pixels per inch. The reason for this is because of the limited number of colors available on a printer. Since there are only so many available colors, there needs to be the ability for more dots to be added to make up for the missing colors. This results in the need for more dots per inch to ensure that the colors work.