Variation: Crop to an exact dimension and resolution

You may occasionally need to crop to an exact dimension and resolution. For example, you may need a headshot that is 1 inch by 1 inch and 150 dpi. To achieve this, select the Crop tool. Notice that the options bar now gives you a place to enter height, width, and resolution. Enter your values. Now when you drag the Crop tool, it will allow only those dimensions.

Make sure that the image resolution is higher than or equal to the one to which you are cropping to avoid sampling up.