Whenever you use an extension cord, you’ll need to know what gauge it is. The gauge determines whether or not the cord will work for your application. For example, to provide the power required to operate a microwave or a refrigerator, two appliances that draw a lot of power, you need an extension cord that can deliver the necessary power.
In this article we discuss a few different 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
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 Length | 0-25 ft | 25-50 ft | 50-100 ft |
|---|---|---|---|
| Amps | |||
| 10A | 14 ga | 14 ga | 12 ga |
| 12A | 14 ga | 14 ga | 12 ga |
| 15A | 14 ga | 14 ga | 12 ga |
| 20A | 14 ga | 12 ga | 10 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.
