Difference Between DPI and PPI

DPI and PPI are terms that are often used to relate to the clarity or resolution of an image. These terms are frequently used by photographers, TV manufacturers and those involved in printing images using printers. Many seem to use these terms interchangeably which is wrong as despite similarities, there is a great difference between DPI and PPI. DPI is an old term that was commonly used to refer to resolution of an image while the new term is PPI which is more specific for what it means. This article will explain the two terms and remove any doubts in the minds of the readers regarding their usage.

What is DPI?

DPI means dots per inch and is actually a feature of a printer as to how many dots it can print in one square inch paper. These dots make up an image. Higher the concentration of dots in an inch, higher is the resolution of the photo, which is why printers having a high DPI can produce more sharp and clear images than printers with a low DPI. If you see 1000 DPI on a printer, it simply means that the printer can produce 1000 dots per inch of the paper.

What is PPI?

PPI stands for pixels per inch and is referred to a quality of a photo that has been captured by a camera. Every camera today comes with the number of mega pixels it can produce in a photo. PPI is a number that depends both on the mega pixels of a camera as well as the size of the photo. This will be clear by this example.

Suppose you have a photo that measures 6 x 4 inches and you have shot it with a camera with a 5MP sensor. The size of the paper is 6 x 4=24 square inches. Dividing the number of mega pixels sensor supports with this number will give the number of pixels on per square inch of paper. In this example it is 5/24. Now all you need to do is to find out the square root of this number to find out the PPI of the image. In this case it is 456 PPI.

When printing a photo through a printer, it is better to ensure that the DPI of the printer is higher or at least equal to the PPI of the image as otherwise the photo printed by the printer will not be as clear or sharp as it is originally.