15.24 cm.

It is 15.24 cm. The inch we are talking about refers to inches in the imperial system, 6 inches is 6 inches, and 1 inch = 2.54 centimeters, the diameter of 6 inches is 6×2.54=15.24 centimeters. This inch is basically used in construction, mobile phones and computers.

The diameter of the 6-inch cake is 15.24cm. Based on the calculation that one inch equals 2.54 centimeters, the diameter of a 6-inch cake is approximately 15.24 centimeters. 6 inches refers to the base of the cake, excluding cream and other decorations. After a layer of fresh cream is added to the cake, it will generally increase by about 1 cm.