If the background isn't important, you could use the crop tool. It the tool options, you can specify a width, e.g. 2", and crop it right down.
There is also the Measure tool (hold down the eyedropper tool to see it). This can be used to tell you the current size of the object, and with a few simple calculations, you should be able to work out how much to resize the image to get the dimensions you need. For example, if you measure your 2" object, and it's 1" in Photoshop, then go to Image > Image Size... Change the width units to "percent", and enter 200%.