Most medicine cabinets are usually made fit over a sink and hence it is common to see them somewhere about 20 inches wide and 24 inches high. Medicine cabinets that are surface-mounted can protrude about 6 inches.
Some cabinets are designed span a wide counter area. These can be around 50 cm long and 26 cm high. Smaller long cabinets can be 40 inches long and 26 inches high. There are also boxer styles that measure 23.75 inches by 26 inches. In addition to these options, you also have oval designs that can measure 25 inches by 32 inches.
Start with to find out which size is best for your space Measure the expansion of the wall where you want to place the cabinet. That will tell you what type of space to work with. From there, the shape is a matter of personal preference. You will notice the right design.