Knowing the right size battery for your small electronic device should be easy. It is either on the existing battery, around the battery compartment, or in the user's manual. Here are the most popular types of button cell batteries, used in quartz watches, calculators, and PDA devices.
*1.5V
*1.55V
*3V
*CR2032 has a diameter of 20 mm and a depth of 3.2 mm.