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4 Ways to Tell What Gauge an Extension Cord Is (Plus Many More Tips)

tips how to find extension cord gauge

How To Determine Gauge of An Extension Cord

Determining the gauge of an extension cord is crucial for ensuring optimal performance and safety. Gauge refers to the thickness of the conducting wires within the extension cord itself, which directly impacts its power capacity and electrical resistance. You can follow these steps to accurately identify the gauge of your extension cord:

  1. Locate the markings on the cord: The gauge is usually specified alongside the number of conducting wires. For instance, a “14/3” cord has 14-gauge wire and three conductors inside.
  2. Understand the gauge numbering system: Lower gauge numbers indicate thicker wires, which can carry more current and have lower resistance. A higher gauge, on the other hand, denotes thinner wires with reduced power capacity and increased resistance.
  3. Consider cord length: The length of an extension cord affects its power capacity as longer cords exhibit higher electrical resistance. For optimal performance, select an appropriate length for your needs, and avoid connecting multiple cords together.
  4. Assess the cord’s amperage: Amperage (A) is another critical factor in determining the cord’s power capacity. Heavier loads require cords with higher amperage ratings. Ensure your extension cord meets the amperage requirements of the devices you plan to use with it.

By understanding and considering these factors, you can accurately determine the gauge of an extension cord and ensure safe, efficient use. Remember to choose cords that are suitable for your specific power requirements and intended usage, as well as adhering to any applicable safety standards.

In this article we discuss a few additional methods for finding out how to tell what gauge an extension cord is to make sure you use the right one.

Related: How To Store Long Extension Cords

Additional Tips on How to Tell What Gauge an Extension Cord Is

There are a few simple ways to tell what gauge an extension cord is. They are:

  • Read The Box or Packaging Label
  • Examine the extension cord itself
  • Look at the thickness of the extension cord
  • Cut open the extension cord

Check the Box

If you just bought the extension cord, there’s a very good chance that the gauge will be printed on the box. It is typically printed alongside some more specifications about the wire.

If you don’t have the box handy, then let’s keep trying other options.

Examine the Cord

In some cases, you can just take a look at the extension cord itself. There should be printed numbers and letters that probably don’t make any sense at first glance.

If you find text that says something like “12/3” then that means you’re looking at 12-gauge wire that has 3 wires in it (the ground, neutral, and hot wires).

If you see text that says “16AWG” or “AWG16x2C”, then the 16 stands for 16-gauge wire. In the second example, 2C means that it has two wires (no ground).

If the cord doesn’t have stamped or printed text somewhere, you should be suspicious. Low-quality manufacturers omit this detail, and you might be putting yourself at risk by using the cord.

Use the Thickness

Another shot you can take is to try to compare the thickness of your extension cords. If you have multiple cords of the same length that are all different gauges, then they’ll be different thicknesses.

The higher-gauge cord will be the thinnest option in the lineup. This won’t tell you the exact gauge in your cord, but it will help you line them up in order of gauge.

Cut it Open

If you’re looking to replace an extension cord and you can cut the old one open, it might help you out. Measuring the wire will tell you what the gauge is. For this, you’ll need calipers or mics to get an OD of the thin wire.

This option won’t help everyone, but it might help you. The diameters are as follows:

18-gauge is 1.02mm, 16-gauge is 1.29mm, 14-gauge is 1.63mm, 12-gauge is 2.05mm, and 10 gauge is 2.59mm.

What is Wire Gauge

You might already know this, but simply put, the gauge of a wire is just how thick it is. Most extension cords will range from 10-gauge to 18-gauge with some exceptions. The lower the number, the thicker the wire is.

That means that a 10-gauge wire is thicker than a 18-gauge wire. Lower-gauge wires allow for higher currents.

Wire Gauge and Amperage

As wire gauge increases, it’s able to carry more current, or amperage (amps). Larger tools, such as table saws and air conditioners will draw more amps. So in these kinds of situations where more amps are required you would use larger gauged wire.

Current (amps), Wire Gauge and Extension Cord Length

If you know the rated current on your extension cord, you can find out what gauge it is – it all depends on the length, though. This is also a good time to remind you that the length of your extension cord will determine how much current the wire can handle. The longer a cord is, the less current it can handle compared to a shorter length.

Cord Length0-25 ft25-50 ft50-100 ft
10A14 ga14 ga12 ga
12A14 ga14 ga12 ga
15A14 ga14 ga12 ga
20A14 ga12 ga10 ga

25-Foot Length

If your extension cord is a 25-foot length and the current is 10A, 12A, 15A, or 20A – you have a 14-gauge wire.

50-Foot Length

For a 50-foot cord, if the current is 10A, 12A, or 15A – you have a 14-gauge cord. If the rated current is 20A then your cord is 12-gauge.

100-Foot Length

Finally, if your 100-foot cord has a rated current of 10A, 12A, or 15A – you have a 12-gauge cord. If the rated current is 20A, then it’s 10-gauge wire in your extension cord.

Figuring Out Wire Gauge By Using Extension Cord With Tools

You might fall for the trap of current draw. If you’re using a saw that requires 15 amps with an extension cord and it’s working, you might wrongly assume that your cord is rated up to 15 amps.

It could be that you’re using an undersized cord that’s straining to run your tool. This could give you a wrong idea about the wire gauge of this cord. Don’t assume the gauge just because the cord powers a certain tool or item.

Pro Tip: Most, if not all power tools will have a sticker, plate or placard on it that tells you how many amps it requires. Use this to determine what gauge extension cord to use.

Using an Undersized Extension Cord

Using an undersized extension cord is bad for a lot of different reasons. First off, it can lead to a lot of heat and a fire if it’s used for an extended period of time. Since the wire isn’t large enough to carry the current, it will overheat. If the wire is in a coil, then it will heat up even faster.

If you’re running tools on an undersized extension cord, you’ll burn out the motor on your tool. Since the tool isn’t getting enough current, you’re starving the motor. That means that your tool’s motor will wind up working too hard and it will exceed the designed limits.

12 Gauge vs 14 Gauge Extension Cord

When comparing a 12 gauge vs 14 gauge extension cord, it’s essential to consider both the length and the intended amperage. For a 100-foot cord, a 14 gauge is suitable for devices requiring 11-13 Amps, while a 12 gauge is ideal for those needing 14-15 Amps. If your extension cord is 150 feet long, the 14 gauge can safely handle 1-7 Amps, and the 12 gauge is designed for 8-10 Amps. The length of the extension cord plays a crucial role in determining its capacity, with thicker cords (lower gauge) supporting higher amperage and longer distances, ensuring optimal performance and safety.

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