How to Identify Electrical Wire Gauge

What You'll Need
Current tester
Wire strippers
Electrician's pocket reference manual

Knowing the gauge of electrical wire is incredibly important to an electrician. This is what tells an electrician how many amps any one wire can actually conduct through the line. If the voltage you are trying to pass through a specific wire is more than the electrical wire gauge, you run the risk of shorting out the line or causing an electrical fire. Your home requires much more electricity than your stereo speakers; this is the reason why a cable running from a utility pole is much larger than a speaker wire. This article will show you how to identify the electrical wire gauge yourself.

Step 1 - Expose the Wire

Before you expose the wires in any circuit box or outlet, always make sure that the power is turned off at the main junction box. Never touch a wire with your bare hands until you are completely sure that the wire has no current running through it. After cutting the power, use current tester to determine if the line is still hot or not.

You will first remove the face plate or the cover of the circuit to get to the wires themselves. Inside, you will see several wires attached to the circuit. Use the screwdriver to loosen them.

Step 2 - Determine the Size of the Wire

The insulation around the electrical wire offers little help to you. The colors are used to identify the polarity of the wire, the most common being red, black, and yellow. However, wire strippers have multiple holes labeled with dimensions where you can insert the wires. You not only can strip wires of a specific size but can also determine the circumference of the wire.

Insert the end of the wire through one of the holes of the wire stripper. You want the wire to be able to move in and out of it with ease. Gaps around the insulation indicate you are using a hole that is too large. If the wire goes through a hole with force, the hole you are using is too small. Once you find the right one, look at the number on the wire stripper. This is the size of the wire.

Step 3 - Determine the Electrical Wire Gauge

When you know the size of the wire, you can consult the reference manual. Most electrical manuals list electrical wire gauge not only by size but also function. Take note if the wire was inside or out, insulated or not, weatherproofed or not, or any other possible environmental circumstance. With this information, you can begin thumbing through the pocket manual until you come to the correct section for the wire type. You can then scan the pages for the size of the wire and subsequently the electrical wire gauge.