So, if you have a bedroom door that is 30″ wide (which is considered a 2/6 or 2′-6″ door) just add 2″ to the width and frame it 32″ wide. The height is 80″ (which is considered 6/8 or 6′-8″) add 2-1/2″ to the actual door height and frame it 82-1/2″ high.Click to see full answer. Regarding this, how big should a door opening be?The height for all passage doors must be a minimum of 80 inches and the standard width sizes for interior doors are 24”, 28”, 30”, 32” and 36”. The minimum recommended door width to allow persons with disabilities’ to pass through is 36 inches.Likewise, how big should the opening be for a 36 inch door? The doors are also a standard 80 inches tall. Presuming the door is a 36-inch wide door, the dimensions of your opening should be 37½ inch wide by 81½ inch tall. Similarly, it is asked, how much smaller should a door be than the opening? Using the Measurements Prehung doors make installation much simpler. For a slab door installation, however, you will find that the door fits best if you make it 2 1/2 inches shorter and 2 inches narrower than the rough opening.How big is a 32 inch door? Standard interior door width is 32 inches. This is the minimum width required for a passage door.