The size of the seven-inch touch screen is 17.78 cm.
The size of the touch screen refers to the diagonal of the screen, and the seven-inch touch screen refers to the distance of the diagonal of the touch screen is 17.78 cm. If the 7-inch 16:9 screen is 15.5 cm * 8.7 cm, if the 7-inch 4: 3 screen is: 14.2 cm * 10.67 cm.
Internationally, 1 inch is equal to 2.54 cm. Seven inches is 7*2.54 cm, which is a seven-inch touch screen with a size of 17.78 cm.