How to get the width / height of an element in Photoshop?
When you make a selection, the 'Info' panel should show the width (W:) and height (H:) of the selection. It has to be the active selection, though.
Note: The active selection "marching ants" don't show up in the screen capture.
If you activate the transform tool on a layer (CMD+T or CTRL+T), you'll see that in the top panel, the X/Y position is shown along-side the size, angle, etc.
The size is in Percent by default, but right-clicking the field gives you a selection of measurements to pick from, Pixels, in this case.
