Can you use an Extension Cord with a Welding Machine?

Last Updated on May 17, 2022

Extension cords have become so indispensable to our work, school, and domestic setups of tech equipment that it is difficult to imagine a time or situation where we won’t need them.

Like everybody else, it is common (perhaps even more so in this case) for welders to find themselves a bit too far away from their electrical sockets while performing their welding operations; this means that just like everybody else, welders have to make use of extension cords every now and then.

Except, in welding, it is not so simple. Welding machines draw extremely large amounts of current when they’re being used, so you can’t just use any extension cord for your welding operations; you have to get special extension cords that can stand through the immense electrical load that welding operations require.

If you’re interested in learning about the different kinds of extension cords that are suitable for welding, you’ve come to the right place- stick with us, and we will tell you everything you need to know.

Welder Extension Cord Sizing

The correct size of your cord’s wire will directly depend on the voltage, and current your welding machine exacts. Choosing the correct size of extension wire is important; if a smaller (thinner) wire is used than what is required, you will risk blowing the entire circuit up. This is exactly why minimum-size wire requirements are put within building codes.

To choose the correct wire size, we use charts that let us navigate and find the correct size of wire we need to use. All you need to do is match your welder’s input current and voltage to the corresponding size of the wire in the chart. AWG, or American Wire Gauge, is a U.S. standard for wire sizes. Larger AWG values refer to thinner wires, whereas smaller AWG values refer to thicker wires.

Key Assumptions for Sizing Charts

Before we move on to looking at the size chart, it is important for anyone who reads this chart to be aware of the key assumptions. This section is dedicated to the discussion of such assumptions.

The key assumptions:

  • The voltage will experience a maximum drop of 3%, and the wires in question can withstand temperatures up to 60° Celsius.
  • This extension cord will only power the welder – and nothing else.
  • These calculations only apply to copper wires.
  • The covering on the wires for service applications will be thicker to safeguard the cable inside- this has the added benefit of the wires being able to withstand more heat.

Now that we’ve gone through the key assumptions, you can go through the size chart given below without misinterpreting it.

Power Input Length of the Extension Cord
Amperage Voltage 25 feet 50 feet 75 feet 100 feet
15A 120V 12 AWG 12 AWG 10 AWG 8 AWG
20A 120V 10 AWG 10 AWG 8 AWG 8 AWG
30A 120 / 240V 8 AWG 8 AWG 8 AWG 6 AWG
40A 240V 6 AWG 6 AWG 6 AWG 6 AWG
50A 240V 6 AWG 6 AWG 6 AWG 6 AWG

 

Bear in mind that these are minimum requirements. This means that you can even go for a larger sized wire than what this table recommends.

Ready-Made vs DIY Welding Machine Extension Cord

Ready-Made Cords

The simplest method of obtaining an extension cable for your welding machine is to purchase a ready-made kit.

All you need to worry about is picking a cable with the appropriate plugs that can bear the load on your welding machine (see chart for reference).

For example, 25-foot-long extension cables may use an 8-gauge wire to handle around 50-amp loads – This will be able to bear (rather easily) a 120V welding machine without breaking a sweat. However, be cautious of the advertised ampacity and get an oil-resistant extension cable.

You may also get longer; heavy-duty extension cords might be pricey and quite hefty, but the more amperage you run and the lengthier the extension wire, the more costly it becomes. However, if you’re on a budget or are unable to get the ideal extension cable for your purposes, you have an alternative: make it yourself. This will be the subject of our next section.

DIY Cords

It is surprisingly easy to make your own extension cord. All you’ll need to do is find the right materials and assemble them together. For expert welders, doing this is a piece of cake; however, even non-welders can piece the materials together to build a suitable extension cord.

All you need to make your own extension cord is to get the correct wire and plug from your local electronics market (fairly easy to find). The correct wire size and plug type will depend on the intensity of welding you plan on performing. So, use the chart we outlined for you above to pick the correct materials.

Pro-tip: if you plan on increasing the scale of your welding operations in the future, we’d recommend getting a thicker wire than your minimum requirement. This will allow you to upgrade your welder without having to change your extension cord each time.

When piecing your own cord together, keep these dos and don’ts in mind:

  • Keep the length of your cord as short as you can. The longer your cord, the steeper the voltage drop. This will also generate excessive heat, which can be hazardous
  • Use SOOW wires to make your cord. Cords of this rating are used for heavy-duty industrial applications.
  • Never use a cable whose socket is not grounded- always construct or get well-grounded cables.

Wire Gauge and Amps

The key idea is to choose a cord that can withstand the electrical load of your welder without causing a drastic drop in voltage. Regulatory codes require that every “branch” inside an electrical circuit have a voltage loss of no more than 5%. This includes extension cables. On the internet, you may discover voltage drop calculators that do the computation automatically.

When calculating the voltage drop using such a calculator, be certain to use the welder’s input electrical ratings and not the output values for voltage and amperage. Simply enter 1 for “parallels” unless you want to employ more than one cable to provide energy to the welding machine (extremely unlikely).

Additionally, an extension cable must carry the current necessary by the welding machine without causing it to heat up beyond the wire’s temperature rating.

You may size a wire using ampacity tables to ensure that the temperature during the welding operating stays within the temperature rating. When using the ampacity table, be careful to only focus on the input amps instead of the welder’s output values.

Thus, the wire gauge corresponds exactly to the wire’s capacity to carry the passing current without heating up too much and with a voltage drop of no more than 3%. This means that your circuit breaker will not trip frequently, and your welding machine will operate securely at its total potential. If your wire is too thin, though, even the slightest flux can cause a disaster.


In welding, extension cords are an almost indispensable piece of electronic accessory; however, due to the immense electrical load that welding demands, you need to use special extension cords that can withstand that power.

To choose the right extension cord, you may make use of cord size charts that help you find the correct cord size by checking the corresponding voltage and amperage values.

Extension cords can either be bought ready-made or made at home (much cheaper). Either way, they’re going to serve their purpose, so choose whichever option seems more feasible to you.