Image resolution is the amount of pixels per linear unit in the image and determines the final output size. Resolution depends on the method of image acquisition, i.e., digital camera, scanner, screenshot, etc.
We calculate resolution based on what the final purpose of the image will be. If you want a high-quality, exhibition-ready print, divide your image size by 360.
Example: Image dimensions are 4435x3326. Divided by 360, the print size would be approximately 12x9in.
For more information on image resolution, we recomend reading the guide Image Resolution and Print Size