The size of the hole depends on the size of the exhaust hose. The average diameter of an exhaust hose for a portable air conditioner can vary depending on the specific model and brand of the air conditioner. In general, mobile air conditioners usually have an exhaust hose with a diameter of 12 to 15 cm. Measure the diameter of your exhaust hose and add 0.5 cm. This is the number you enter in the calculator.