At first, cakes were all round, and cakes in cake shops were all inches. The "inch" of the cake refers to inches, so the daily 8-inch cake refers to a circle with a diameter of 8 inches.

The conversion relationship between cake inch (_) and centimeter is: 1 (inch) inch = =2.54CM. So the standard size of an 8-inch cake is 8 * 2.54cm = 20.32cm ..