No matter how many wall outlets you have in your home, chances are there arent enough (especially if you've got an older house) and youre going to need an extension cord or two. And that opens you up to a certain amount of danger. Using the wrong extension cordsor old, damaged cordscan cause fires, damage your tools and equipment, and potentially even kill youthere are an estimated 2,200 shock-related injuries involving extension cords every year.Choosing the correct extension cord for your needs is a necessary step if you want to avoid injury and property damage. There are four things to consider when choosing an extension cord.CodeFirst, you need to make sure youre using the right extension cord for the environment youll be working inare you going to use it indoors or outdoors? In oily conditions (like a mechanics shop)? When buying an extension cord this information will typically be printed clearly on the packaging. but if you bought your cord a while back and cant remember, there is a code printed on every extension cord that tells you all you need to know:S = general useW = weather resistant, outdoor useO = oil resistantFT2 = flame retardantYoull find many other codes, but for most household projects these are the ones you need to know.GaugeNext, you need to make sure youre using the correct gauge of extension cord. Every extension cord has an American Wire Gauge (AWG) rating that describes how thick the wire is inside the insulation. Lower AWG actually indicates larger gauge; most extension cords range from 16-gauge (smallest) to 10-gauge (largest) in two-gauge incrementsyou can find larger or smaller cords, but theyre not common.The gauge determines how much power the cord can handle, measured in amps. Sixteen-gauge cords are suitable for light duty, 10-gauge cords are intended for tools and appliances that pull a lot of power. If in doubt, use a higher-gauge cordits sometimes recommended that the 14-gauge is the smallest extension cord you should use, because its rated for 15 amps, which matches the typical breaker in your homes electrical cabinet. That means your breaker will trip before the extension cord is overwhelmed and overheated.AmpsSpeaking of amps, choosing the right gauge of extension cord requires knowing how much power you need to pull through it. The appliance or tool youre powering will tell you how much power it needs measured either in watts or amps; if its watts, you can easily calculate the amps it needs by dividing by 120 volts (the standard residential voltage; if you know youre on a different voltage, divide by that).Once you know the amps you need the extension cord to handle, select the proper gauge:16 AWG = 10 Amps14 AWG = 15 Amps12 AWG = 20 Amps10 AWG = 30 AmpsAgain, if youre uncertain, a larger gauge cord is better than an undersized one.LengthFinally, you need to know how long your extension cord needs to be. Electricity encounters resistance when it flows, and the farther it has to travel, the more resistance it meets, reducing how much power actually arrives at your tools or appliances. Its always a good idea to get an extension cord thats exactly as long as you need.If you need to run a very long (50-100 foot) extension cord, consider going up in gauge to compensate for the distance.