How to Choose Wire Gauge

Written by david weinberg
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How to Choose Wire Gauge
(Zedcor Wholly Owned/ Images)

The thickness and capacity of electrical wire is referred to as the wire's gauge. Gauge is indicated by a number; the lower the number, the thicker the wire. The thicker the wire, the more electricity the wire can transport. Theoretically, you could use a very low-gauge wire for just about any project, but low-gauge wire is more expensive and also harder to work with. Properly determining the amount of energy that the wire will be carrying will allow you to decide what gauge wire you need.

Skill level:

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  1. 1

    Identify all of the devices that will draw electricity through this wire.

  2. 2

    Search each of the devices for an electrical information panel. This is a small informational note that will explain how much electricity the device uses.

  3. 3

    Look up your device using the web site listed in the Resources section if you could not find the information panel.

  4. 4

    Calculate the amperage draw for each device. If your device has an input measurement such as 2A, then it is a two-amp device. If your device has an input measurement such as 240W, then you need to divide the measurement by the voltage in your house. This is 120V in most cases. A 240W device at 120V would be a 2A device.

  5. 5

    Add up the amperage for each of the devices. Multiply by 1.25.

  6. 6

    Look up your total amperage in the "Maximum amps for power transmission" column of the gauge chart listed in the Resources section. The proper wire gauge is in the far left column. If you are running your wire for more than five feet, you should use a wire one size larger to counter the effects of resistance.

Tips and warnings

  • Always use caution when working with electricity.
  • Be sure to add a circuit breaker or fuse to your new wiring that will trip if the current draw exceeds the amperage you used to select your wiring. If the amperage exceeds the rated amperage for your wire, it can pose a serious electrical hazard.

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