Even though many tablets are advertised as being 8 inches in size, the exact size varies a lot due to different aspect ratios and slight variations. Most 8-inch tablets like the Amazon Fire HD 8, for instance, got a diagonal of 8-inches and are 4.2 inches wide and 6.8 inches high. That translates to a diagonal of 20.3 centimeters and a width and height of 17.2 and 10.8 centimeters. The 7.9-inch iPad Mini, on the other hand, is 6.3 inches and 16 centimeters high, as well as 4.7 inches and 12 centimeters wide.