Two standard voltages are in use around the world: 110/120 and 220/230/240. Most countries in Europe that formerly used the 220 standard have converted, or are presently converting to, 230 volts, which is the standard established by the European Union.

Electrical converters are available to change line voltage from one amount to another. However, there are different types of converters for different types of appliances. Small electronics, razors and non-heating appliances can operate with a 50-watt converter. Heating appliances such as hair dryers, irons, coffee makers and other high-power electrical appliances need a 1600-watt converter. Fortunately, most portable computers are equipped with power supplies that can be used in almost any part of the world.

Three main types of plugs are used: (1) flat blade, consisting of two parallel blades; (2) round pin, consisting of two cylindrical pins, (3) rectangular blade, consisting of one vertical blade and two horizontal blades. Several variations of these basic plugs are in use.

The two-prong flat blade is standard in the United States, Canada, Mexico, and most Caribbean countries, and is also used in some South American and Asian countries, including Japan. An oblique flat blade plug, with the blades tilted inward instead of parallel to each other, is standard in Australia, New Zealand, and China.

The two-prong round pin plug, often accompanied by a third ground pin, is standard throughout Europe and is also found in some South American and Asian countries. The three-prong rectangular plug is standard in the United Kingdom and Ireland. The South African plug is similar to a round pin plug, but larger and with an oversize ground pin.