The Measure/Ruler tool can be a handy little gem when you’re working in Photoshop. To select the Measure/Ruler tool, simply hit Shift + i three times. The reason you must hit they keyboard shortcut three times is that the Ruler icon is hidden two deep in the Eyedropper tool in the toolbox, so you’re hitting it once to activate the Eyedropper tool, and two times to drill down to the Ruler tool. The results of dragging the ruler tool from one point in your document to another is displayed in the Control Bar across the top of Photoshop, as seen in the screenshot above. As a bonus, if you measure something that is at an angle in your document, the degree of rotation automatically appears in the Image>Image Rotation>Arbitrary dialog box for you along with the proper clockwise/counterclockwise rotation setting already set for you.