Every picture you take with your camera or make on an image editing program will have two important numbers related to its size. The obvious one is its height and width. In digital images, this is measured in pixels. Pixels are a relative term however and are difficult to translate to the actual size of a printed document. This is where the second measurement, dots per inch (dpi) or pixels per inch (ppi), becomes relevant. The two of these together can give you the actual image size on your printed document.

Pixels per inch (ppi) and dots per inch (dpi) are similar but slightly different measurements. However, for the purposes of this article we are just going to focus on the printed document which can be used either way. In GIMP, the images are measured in ppi and in Photoshop they are measured in dpi, but the end result is the same.

Both dpi and ppi control how dense the image is. When the dots are densely packed together, such as in a 300+ dpi document, the printed image is going to be much cleaner looking. Your eyes will have more difficulty distinguishing the different dots made by the printer. When the image is less dense it will appear pixelated.

While the picture will be more clear at a higher dpi, the image size will also be smaller. For example, if a photo is 3500 pixels wide and 2800 pixels tall at 300 dpi, it will be 11 2/3" x 9 1/3". The same size image with a dpi of 150 will be twice as big, 23 1/3" x 18 2/3".

To change the dpi and image size you can use any standard image editor. This is normally done when opening a new image but can also be done from the Image tab of both GIMP and Photoshop.



The standard for printing photos is 300 dpi, but this can be made lower if you are willing to sacrifice a bit of quality. The standard for web sites is 72 dpi. This is why even large web images normally print either very small or with poor quality.

For your convenience we have programmed a widget that can calculate exactly what size your photos will be when you change the dpi.

DPI and Image Size Calculator

Enter the photo's information:

Height (Pixels):
Width (Pixels):
DPI:

Just one more helpful tool from Inkfarm.com! If you have questions about DPI and Image Size or other article, feel free to email me at tylergoering@gmail.com