In this lesson you'll learn how to use the Image>Image Size dialog box as a calculator. In the first example, we'll use it to set the resolution of a architectural floor plan so that Photoshop's rulers match the actual size of the rooms that are depicted. Once that's done, you'll be able to use the shape tools in Photoshop to add virtual furniture to the plan, or use the Marquee tool to measure the size of rooms. In the second example, we'll use Image Size to help us make an object in three different photos end up being the same size even though the documents are cropped differently.