When calculating the size of the diagonal door of the refrigerator, subtract 4 from the size of the cabinet and divide it by 2, which is a size of the door. According to relevant public information, when calculating the size of diagonal cabinet door of refrigerator, subtract 4 from the size of cabinet body and divide it by 2, which is a size of cabinet door and a size of opposite door. Usually the length of the cupboard door is 90 cm plus 90 cm, which is 1 m 8.