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a store display of 16 gauge extension cords in orange and green

Wire Gauge

Originally contributed by Jeff Butler • last updated 1/13/2021

The thought of working with electricity can be frightening for some people. But understanding a few basics, such as wire gauge and why it’s important, can not only help you prevent damage to your devices and appliances, it may also prevent fires and save lives.

Definition

The term wire gauge refers to a given number that indicates the size (diameter) of an electrical wire. Gauge sizes are typically measured counterintuitively, with increasing gauge numbers equaling decreasing wire diameters and vice versa. Wire gauge is used to determine the amount of electrical current that can flow through a wire and the amount of resistance it provides. Gauge sizes are fairly standardized under the American Wire Gauge (AWG) system (aka Brown and Sharpe), although other systems such as the Imperial (or British) Standard Wire Gauge (SWG) system are still sometimes used.

Why Is Wire Gauge Important?

Using the proper wire gauge size is important when rewiring or setting up a new electrical circuit because, if the diameter of the wire is too small to handle the amperage, the wire has the potential to overheat and even cause fires:

  • Typical residential wire diameters are designated as a 14 gauge or 12 gauge. However, appliances such as your electric stove, electric water heater, or central air unit may require a 10 gauge, 8 gauge, or even 6 gauge wire.
  • Understanding and selecting the proper gauge size is especially important when using household extension cords (typically 16 gauge). Before plugging in an appliance, such as a space heater, ensure the gauge size can handle the power needed to run the appliance.
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