The result is your door opening depth.

How to measure jamb depth. This measurement is to tell you how thick the. Trim around a jamb is typically referred to as door casing. To get the width, measure from left to right, jamb to jamb.

For height, measure from the. Do it at the top, middle and bottom of the jambs to get three width measurements. Use a tape measure to measure the height of the window from top to bottom in three different places.