Most people have probably seen the terms "DPI" and "resolution" used interchangeably across the internet. The fact is they are related, but are different in meaning when describing an image. DPI stands for "Dots Per Inch" and represents the total number of "pixels" or "dots" that make up an inch in length. Resolution represents the total number of "pixels" or "dots" in the entire image.

Let’s take for example, a 3" x 3" image. If this image was a 100 DPI image, the resolution would be 300 x 300 pixels. Referring to that image as "a 300 DPI image" does not fully describe the image, as it does not identify the vertical or horizontal dimensions which make up the bounding box of the actual image. Referring to that image as "an image with a resolution of 300 x 300 pixels" is also incomplete as it still does not help identify the vertical or horizontal dimensions. A 6" x 6" image at 50 DPI or a 9" x 1" image at 100 DPI both have the same total resolution as our 3" x 3" image at 100 DPI. So you can see here that describing an image only by resolution or DPI can be misleading or incomplete. The proper way to describe an image is to refer to both the image resolution and DPI. If I said "this 100 DPI image has a resolution of 300 x 300 pixels" you would know that it is a 3" x 3" image.

Why is this so important? You may need to adjust an image to fit on a specific size of medium, or you may have a printer that can only print up to a specific maximum DPI. By knowing the exact DPI and resolution of the image, your final results, either printed, or on digital display, will likely encounter less redo’s.  It can also save you money if you are purchasing images, which are typically priced higher with higher resolutions.