Sunday, December 4, 2022

What Size Wire For The Welder Extension Cord?

What Size Wire For The Welder Extension Cord?

You will surely look for extension cords when the plug is located far away from where you need it. It is probably one of the most common ways we use most electric appliances. Even extension cords are common among welders. However, welding requires choosing extension cords very precisely.

An undersized and lightweight cord can definitely become a part of the welding project. However, in the long run, without additional resistance, it might lead to cord melting, short circuit, or even catch fire. There can be massive damage if you don’t choose a welder extension cord correctly.

Whether you are buying or building an extension cord for welders, you must have knowledge about the correct size of wires so that it can easily handle a huge load of current.

Understanding The Sizing of Welder Extension Cord

The gauge or size of the wire required is associated with the amperage and voltage that the welder generally uses along with the chord length of the extension. This is vital that you will also find the minimum size wires available that are provided by Building Code. It also includes the guidelines required.

To make sure that the procedure becomes easy, you can find a proper and simplified chart in the reference. All you need is to match the voltage and amperage of the welder while choosing. Then check the column saying the length of the extension cord and the wire gauge you must use.

You can find the wire sizes are mostly specified by the unit AWG size or American wire gauge. You might find it a little bit confusing, but AWG refers to the science that the wire is stretched and drawn. When you pull wires more times, it gets thinner. So, you always have to bear in mind that when you choose more AWG numbers, you will get the thin wire and smaller AWG means thick wire.

Minimum Size Wire For Welder Extension Cords

Here is a table from where you can find details about AWG depending on the voltage and average of the welder. Welding machines need a proper input voltage to maintain average output and duty cycles. Hence extension cord wire size for minimum voltage drop.

For better performance, NEC or the National Electrical Code recommends the size of the circuit to prevent any voltage drop that exceeds 3%. It has been rated for at least 3% voltage drop and 60 degrees Celsius.


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

Sizing Charts Assumptions

As we have seen, the table mentioned above can be assumed to have a minimum voltage drop of 3% and a 60°C rated wire. To make sure of safety, you can find the biggest wire size specified with rated capacity as almost near or maximum.

Apart from this, when the wire is rated especially for the higher temperature, the amount of amps it is capable of passing might also be a lot higher.

These are the calculations for assuming that the extension cord will have the ability to power the welder. However, if you try to add something else apart from a welder on this power cord, you might need help to be able to apply everything mentioned in the table. The recommended gauges are specifically for copper wire.

While evaluating the temperature rating of wire, there is a need to make sure of building things that ensure safety. Making use of wire jackets for service applications can improve the protection of the cable. Therefore, it will also have the capability of holding more heat compared to other wires.

Lastly, using thicker wire means choosing a gauge number with a low AWG than the recommended one but not using a wire with a higher AWG gauge. The table will help you understand a proper recommendation.

Difference Between Build Your Own Welder Extension Cord Vs Pre-Made Extension Cord

Let’s check pre-made welder extension cords.

Pre-made Cords

One of the best and simplest ways of getting extension cords for welders is by buying pre-made products. You just have to find the cord which will be able to handle a load of welding along with the correct plugs. However, you have to be vigilant about the mentioned ampacity and ensure that the cord is oil-resistant.

For example, if you are choosing a heavy-duty extension cord of 25 feet, it uses 8 gauge wire and has the capacity to handle 50 AMP load. Therefore, it will be easily able to take 120 Volts welders without any problems.

The market already has a huge range of cord available in different lengths. The cord of 50 feet makes use of 8 wire gauges and has the capability of handling 30 AMPS on 240 or 120 V supply.

However, if you are willing to run a 250 V welder on the higher AMPS, you will require a cord of 5 feet with 6 wire gauges for handling it. If you need a much longer cord, 75-foot size can be a good choice which is manufactured with 8 wire gauges to carry 40 AMPS at 240 volts. You can stay sure that it will not overheat or face large voltage drops.

You will also be able to find even longer and heavy-duty cords which are 100 feet long. These are manufactured with 6 wire gauge, which is able to transmit 50 A at 240 V. This might be very heavy and expensive, but when you choose to run on higher amps, the longer the extension cord and so will the price.

However, if you’re not able to find a perfect extension cord or you want to save some money, you definitely have another option of building your own extension cord.

Building a Desirable Extension Cord

It is not tough to create your desirable extension cord. The plug and wire end you need is definitely easy to find. Besides, you can easily put them together. Being a welder is something most welders can easily do. However, since sizing wires can be tricky, you must be very careful.

If you have the plan to add a bigger welder, you might like to create your own extension cord. It will be able to handle the future loads you need. So, oversizing the extension wire can be done, but you must keep in mind, not to undersize the required gauge.

Follow These Tips:

  • The first important thing is to use a short extension cord. Remember, when it gets longer, it has the chance of high voltage drop generated heat.
  • Making use of SOOW wire is another essential requirement. All the cables that have the rating are mostly created for heavy-duty applications with improved durability and flexibility. The wires that have SOOW designation have the ability to handle 600 V with internal and external world insulation.
  • Do not use Romex. These are the single-stranded wires not intended explicitly for frequent rolling up. When you constantly handle and bend the wire, it can break or become a hazard for you. Apart from this, it does not have a durable covering to take this spatter and abuse.
  • Eventually, it is always a great choice to manufacture and install grounded cables. Do not use a socket or cable which has not been grounded.

Gauge Size & Amps – Why Do They Matter?

To be precise, the wire present in the extension cord must be thick enough so that it can easily carry the load without resulting in a huge voltage drop. The NEC is a specification of voltage drop. It has already been specified that it should not be more than 5% in the electrical circuit. You can also take the help of the internet by finding a voltage drop calculator to make the calculation yourself.

For calculating voltage drop, you have to make sure about the electrical input ratings for the welder, not the voltage or output current. For parallels, you can enter 1 unless you are sure you will use more than one cable to feed juice to the welder.

The extension cord must have the capacity to carry the required amperage by the welder without the need for heating above the rated temperature of the wire. Probably the 60°C limit is considered safe on the lower end. However, most wires have ratings for higher temperatures.

As the wire gauze is directly associated with the ability of the wire to handle amperage without overheating, it is a mandatory aspect to check. This also means that the circuit breaker would not pop every 10 minutes and you will be able to operate it without facing any challenges.

Do’s & Don’ts For Extension Cord Success


  • You must understand the amount of current the welder draws.
  • The size of the circuit breaker for the welder.
  • You have to make use of building wire and the outlet recording to the size of the breaker to protect it.
  • You have to make sure about the length of the wire gauge and the current it requires.
  • Make sure to maintain a short extension cord with a bigger practical gauge.
  • Roll the extension cords to prevent heat from building up.


  • Do not use solid wire or Romex as the portable extension cord.
  • When you repeatedly uncoil and coil the extension cord, it can damage the solid wire.
  • The covering eyes are not good enough and can get damaged easily by spatter.
  • Do not use an extension cord that has a lower amperage rating compared to the circuit or welder.
  • Do not coil the extension cords while using.
  • Do not make use of cords that have no ground plugs.
  • Do not run over one tool on a chord.
  • Do not choose longer extension cables when you already have shorter ones.


Whether you plan to use a pre-made extension cord or manufacture your own, it is always a mandatory thing to choose the right wire gauge. It will prevent any type of damage to the equipment and keep you safe throughout.

The current amount simply determines the wire gauge you need, the voltage of the welder draws, and the extension cord length. There are several ways of figuring out the required wire gauge, which includes asking online forums. Hopefully, the table provided in this article will offer you the reference that you need and helps you to choose the correct welder extension cord.


Related Articles


Please enter your comment!
Please enter your name here

Latest Articles