All electrical wire is numbered according to size, using a rating system called the 'A-W-G,' or American wire gauge. In this system, the bigger the wire, the smaller its number. Though this may sound confusing at first, just remember, wire size works opposite of what you would expect. The size of wire needed will depend on the amount of current it has to carry: a big appliance like a dryer might take a number eight or number six wire, while most standard outlets need only a number twelve. It's important to use the right size wiring for each particular application: an overloaded wire will get extremely hot, and could even start a fire. This is of special concern in older homes, where the wiring may not be adequate to handle today's abundance of electrical devices. If you have questions about the wiring in your home, consult an electrical expert.