Accurate measuring for a recessed medicine cabinet ensures you buy a unit that fits inside the wall cavity perfectly. If you are installing a new recessed cabinet, measure the opening once you have the hole cut out and know what is behind the wall. Most homes will accommodate a 4-inch deep recessed cabinet, however some older homes might take one that is a little deeper. The more precise your measurements, the less work is necessary for trimming out the cabinet to hide the hole.
Remove the old recessed cabinet, if you are replacing one. You must measure the actual hole in the wall to ensure proper sizing. Most cabinets use screws to secure them into wall studs, with the screw heads visible inside the cabinet. Use the appropriate type screwdriver to remove the screws.
Measure the width from the top left to the top right of the opening with a tape measure. Measure the width at the bottom of the opening in the same manner. Use the smaller of the two measurements as the width for ordering your recessed medicine cabinet.
Position the end of the tape measure at the upper right corner, and measure down to the inside of the lower right corner. Repeat the measuring on the opposite side. Use the lesser of the two measurements as your height.
Place the tip of the tape measure against the back of the opening on the lower left corner, and measure to the edge of the outer wall. Usually, this is the thickness of the drywall along with the width of the wall stud. Repeat this process at all four corners to obtain the depth measurement for your recessed cabinet.