average height of a bookcase
1. For ease of shelf access, bookcases are generally no higher than 84 inches. Small bookcases are usually 30 to 42 inches high. The highest shelf in a bookcase should be as high as an average-sized person can comfortably reach â about 72 to 78 inches.If the shelves will be accessed from a sitting position, the highest shelf should be no more than 60 inches above the floor. The lowest shelf should be 3 to 4 inches from the floor level.2.he highest shelf in a bookcase should be as high as an average-sized person can comfortably reach â about 72 to 78 inches. If the shelves will be accessed from a sitting position, the highest shelf should be no more than 60 inches above the floor. The lowest shelf should be 3 to 4 inches from the floor level. 2.