They require the same 24-inch depth and 35-inch height opening of a standard dishwasher, but they require much more width. The most common width for an oversized dishwasher is 30 inches, but they are available in widths as large as 42 inches.Typically, however, an oversized dishwasher must be specified at the time of the cabinet order to accommodate the extra width in the design.he vast majority of undercounter dishwashers measure approximately 24 inches in width, 24 inches in depth and 35 inches in height with adjustable feet. This means that the rough opening in your cabinets must be 24- by 24- by 35-inch.