: Calculator refers to a calculating device. A small hand-held notebook type object that has a display unit. Currently most calculators are digital and use LCD screens. They need very little power or battery. Notice that the watt on the back of the calculator is written as watt which is 0.004 or less, which means 4 parts of 1000 watts of 1 watt of current / ampere consumed in one hour. That means it will take 2/3 years to finish 1 good pencil battery.