NEC, THHN & AWG Wire Gauge Ampacity Rating Chart: 0, 2, 4, 6, 8

If you have been to an electrical store, you will notice electrical wires come in several sizes. Most people would think that it does not matter and is pure aesthetics. Its size greatly depends on other things, such as the electrical current passing through. We will be going through the different products in the following sections using the American wire gauge system. Each section is conveniently named, so you can quickly use your browser’s search function to jump to the section you like.

Whether you’re doing gasless MIG welding or welding aluminum, you must choose the one that is right for your project.

THHN vs. THWN

Wires being installed

When looking at electrical wires, manufacturers use different types of material for the coating. The most common types are the Thermoplastic High-Heat Nylon-coated (THHN) and THWN. It stands for “Thermoplastic Heat and Water-resistant Nylon-coated”. Suppose you think about how these two are different. The THWN can operate in an environment similar to the THHN without using additional accessories. The Thermoplastic Heat and Water-Resistant Nylon-coated wire is a better version of the THHN. You can still find both across different infrastructures.

Thermoplastic High-Heat Nylon-coated (THHN)

The Thermoplastic High-Heat Nylon-coated wire is probably the more common option between the two. You can find this product in almost any building, whether commercial or residential. It comes in either a stranded or a solid wire, depending on the size. It uses either aluminum or copper as conductive material. Finally, polyvinyl chloride (PVC) wraps the conductive material and serves as insulation. THHN rates at 75°C in a wet location or 90°C in a dry location. Several options of this type carry a dual rating cable, which you can identify by a THHN / THWN marking.

If you think about distinguishing this from other types, you will observe its PVC insulation. In most cases, it uses a thinner one. It is important in electrical properties to determine its amp rating. A negative effect of having a thin insulation layer is frequent current leaking, leading to a breakdown. When the insulation in THHN burns, it releases toxic smoke. It is highly undesirable.

Since this type uses nylon coating, it is not extremely flexible. It becomes an issue for some people, especially those who want to maximize saving time and energy during installation. Despite its cons, the THHN is still very popular because it is cheaper. When you plan to wire an entire building, you will want to save money whenever you can. Having a cost-effective solution without sacrificing safety goes a long way, which is why several people still go for a THHN.

Thermoplastic Heat and Water-resistant Nylon-coated (THWN)

Braided NEC cable

Thermoplastic Heat and Water-resistant Nylon-coated is the least common between the two. According to the National Electrical Code, you can mostly find this type in industrial and commercial buildings. Its outer layer is tough yet easy to pull and bend. When installing it, electricians will not have a hard time bending it. It saves them time and energy in the long run. The THWN is also resistant to common chemicals, such as gasoline and moisture.

Unlike THHN, you can commonly find the THWN in alternating current electrical distribution systems across the country.

It can be used during the installation of a range of things, including:

  • machine tools
  • conduits
  • feeders
  • controlled circuits.

These systems typically have voltage levels that range from 110 volts to 600 volts. It uses copper or aluminum conductors, either solid or stranded.

It is suitable for use up to 90°C temperature in dry and wet locations. When it comes in contact with oil or coolant, the suitable temperature you can expose it to decreases to 75°C.

The THWN wire has approvals from several laboratories and regulatory boards, including:

  • the Canadian Standards Association
  • Underwriters Laboratories
  • American Society for Testing
  • Materials Miscellaneous
  • Restriction of Hazardous Substances Directive

Standard wire gauge chart

This section only serves as a guide when looking at a gauge chart. If you plan to install anything involving electricity, always call for a professional electrician to handle the work for you. It is important to know about the right option for your needs. Electricians in different regions reference different charts, but this section is for the United States.

breaker next to wires

The easiest and quickest way to determine the size you need is to use a standard wire instrument. In the United States, we use the AWG. It is otherwise known as the American Wire Gauge system. It defines the diameter, commonly known as the solid round wires. On the other hand, the ampacity defines the certain type’s highest current.

The table below shows that the AWG value is opposite the diameter. It means a higher AWG value would mean a smaller size. For example, a 12-gauge option can carry a higher amp than an 18-rated one. We defined the diameter in inches and millimeters to make it easier.

To quickly summarize the chart, the 0000 AWG has the largest diameter. The 40 AWG has the smallest diameter. A smaller diameter lets less energy compared to a larger diameter. For more details on the diameter of each AWG, you may refer to the chart below.

AWG Diameter (inches) Diameter (millimeters) 
0000 0.46 11.68 
000 0.4096 10.4 
00 0.3648 9.266 
0.3249 8.251 
0.2893 7.348 
0.2576 6.544 
0.2294 5.827 
0.2043 5.189 
0.1819 4.621 
0.162 4.115 
0.1443 3.665 
0.1285 3.264 
0.1144 2.906 
10 0.1019 2.588 
11 0.09074 2.305 
12 0.08081 2.053 
13 0.07196 1.828 
14 0.06408 1.628 
15 0.05707 1.45 
16 0.05082 1.291 
17 0.04526 1.149 
18 0.0403 1.024 
19 0.03589 0.9116 
20 0.03196 0.8118 
21 0.02846 0.7229 
22 0.02535 0.6438 
23 0.02257 0.5733 
24 0.0201 0.5106 
25 0.0179 0.4547 
26 0.01594 0.4049 
27 0.0142 0.3606 
28 0.01264 0.3211 
29 0.01126 0.2859 
30 0.01002 0.2546 
31 0.00893 0.2268 
32 0.00795 0.2019 
33 0.00708 0.1798 
34 0.00631 0.1601 
35 0.00562 0.1426 
36 0.005 0.127 
37 0.00445 0.1131 
38 0.00397 0.1007 
39 0.00353 0.08969 
40 0.00314 0.07986 

Is it dangerous to use the wrong one?

The short answer to this question is yes. It is dangerous to use an incorrect size. The same way you want to avoid unnecessary danger if you’re welding, you’ll want to make the right electrical choices.

A common misconception is that there won’t be any issues as long as the wire fits with the connector. When dealing with circuit breakers, pay much attention to the wire. Those unaware often use an AWG below the recommended rating because it is cheaper. They think it won’t make any difference. In the long run, getting a smaller one than what you should be getting will only cost you more.

Professional electricians often recommend using a larger rating for your circuit breaker. You will greatly reduce the chances of using the incorrect option. You don’t want to pick one that can’t handle the necessary amount of amps you’re dealing with. Picking a bigger one will not negatively impact performance or safety. The only negative effect it has is on your budget, which will cost you more than using a substandard option. Looking at it in the long run, you can save more because you will unlikely run into damages with your circuit breaker.

How to choose the right one?

Electrician working on different NEC wire sizes

It is important to know about compatibility across different scenarios when dealing with electrical components. Choosing an incorrect size could lead to burning or fire at worst. People think that it does not play an important role, but it does. Pick the correct one to prevent any accidents from happening.

When dealing with a circuit breaker setup, extra precautions need to be in place. For example, the AWG needs to be compatible with the circuit breaker you plan to use. One that is too small for the circuit breaker could lead to a drop in performance. At worst, it can start a fire.

In the following sections of this article, we will discuss the maximum amps a particular AWG can support. If you have an 8-gauge, will a 30 amp circuit breaker work with it without any issues?

Wires sizes

Whether you’re looking for the ampacity for AWG wire 6 through 26, you can find it in the section below. All the corresponding numbers refer to the gauge.

0 (1/0)

There is a general rule of thumb when choosing an AWG wire. You need one that can handle your amp requirements. It can handle any amount of amperes below its maximum capacity.

For the 0 (1/0) gauge, the maximum amperes it can handle is 150 amps. It means it can handle any amount of amps as long as it is below its maximum capacity. Typically, you can use it as a cable for your car audio.

2/0

You can use a 2/0-gauge copper wire for a maximum of 190 amperes. It can handle anything below its maximum capacity without any issues. If you own a sailboat that operates with a battery, you can replace any wire connecting to the battery. 

3/0

A 3/0-gauge supports a maximum amperage capacity of 239 amps and can handle anything below its maximum capacity. A 3/0 is perfect to use with a portable solar setup, allowing you to get the most amps. 

1

If you have a 1-gauge product, it supports a maximum of 119 amps. Any device that needs 119 amps of current or below will work fine with this type of product. 

2 Gauge Wire

A 2-gauge wire supports a maximum capacity of 94 amps, which means it will work just fine for any device that needs less. It is good to use this for relocating your car battery. You can also use it to install amplifiers and high-powered car subwoofers in your vehicle.

3

You can use a 3-gauge for a maximum of 75 amps. It can also support any device below 75 amperes. It is good to use this in your main panel or subpanel at home. Be sure your electrical system at home has a ground wire. Hence, excess electrical charges have a safe place to travel in case. 

4 Gauge Wire

A 4-gauge wire is otherwise known as the 4 AWG. It supports a maximum amperage capacity of 60. This has a wide range of applications. You can use it for your audio devices, such as a subwoofer or amplifier. It’s also great for off-grid systems, such as a solar panel system or welding applications. 

6 Gauge Wire

If you have a 6-gauge wire, it can support a maximum of 37 amperes. It can also support any device that needs less than 37 amps. It is good to use with almost anything that involves automotive. If you plan to use this in an automotive, be sure to consider motor vibration. Over time, it could cause it to break. Be sure to provide enough isolation and strain relief.

8

An 8-gauge, also called 8 AWG wire, supports a maximum amperage capacity of up to 24 amps. This is good to use with some of the following:

  • batteries
  • lamps
  • household appliances
  • meters
  • model cars
  • planes
  • and electric heating appliances.

9

If you have a 9-gauge, it can support a maximum of 19 amperes. It is ideal to use this for a 4-channel amplifier to speaker installation. 

10

A 10-gauge can support a maximum of 15 amps. This is useful for a range of household appliances. It can also be used for electric heating appliances and lamps.

12

If you have a 12-gauge, it can support a maximum amperage capacity of 9.3 amps. You can usually use this in connecting an amplifier with a subwoofer. Certain things like lawnmowers and leaf blowers may also use this type, assuming they are corded rather than using gas.

14

A 14-gauge supports a maximum ampacity of 5.9 amps. It also supports anything below 5.9 amps. It is good to use it for your car audio system or home theater system.

16

A 16-gauge supports a maximum of 3.7 amperes and can handle any device below it. Typically, you can find this amount of current in aluminum batteries or RC batteries. It’s also what is used in LED lighting. 

18

You can use an 18-gauge wire with any device that needs 2.3 amperes or less.

20

A 20-gauge supports a maximum ampacity of 1.5 amps, which means it can handle any device that requires less than 1.5 amps. You can widely use this in RC batteries or LED lighting.

22

A 22-gauge can handle a maximum of 0.92 amps. It is good to use it in RC and LED lighting. 

24

If you have a 24-gauge, it can handle a maximum of 0.577 amps.

26

A 26-gauge can handle a maximum of 0.361 amps. In most cases, you can use this for gate openers. However, be sure to check the current requirements before getting one.

28

A 28-gauge can handle a maximum ampacity of 0.226 amps, which means it can handle any device with a smaller amps requirement. This is good to use with aluminum batteries and LED lighting at home.

Make sure also to check out this post that has the NEC table. We also have various articles on ThermoKing fault codes and welding joints.

We have written extensively on the topic of electrical safety because it is potentially something that could harm your family. You may be standing at Home Depot thinking wanting to buy the cheapest option available. You should know that it may not be the best decision. On top of that, using an extension cord that’s not rated for your intended use could void the warranty of your expensive tools!

wires in the wall

FAQ

What is the difference between THHN and THWN?

These are two different wire standards. They’re very similar and can usually be used interchangeably. The biggest difference is their water resistance. It means THWN can operate in higher temperatures if conditions are wet.

How do I calculate what size wire I need?

Add up all the amps that you will need to run. A lawnmower will have different requirements from a generator. Once you know the amount of power you need, you’ll want to find a wire size chart.

What size wire do I need for 100 amp?

2-gauge.

How do you determine wire rating?

The best way to determine wire rating is by using the NEC chart.


How many amps can 10 Thhn wire carry?


THHN wire refers to thermoplastic high heat nylon wire. This type of wire is made from PVC or polyvinyl chloride insulation. It also has a heat-resistant jacket made of nylon, making it even more popular. The bestseller of this wire is the size 10 gauge. 10 gauge THHN wire can carry 30 amps of current.


What size THHN wire is good for 100 amps?


Even within THHN wires, there are two popular materials – copper and aluminum. If you’re going for copper option #4, THHN wire is the optimum size for 100amps. However, you’ll want a size 2 THHN wire in the aluminum.

If you’re renovating or building a new home, you’ll need to know your electric game well. In this case, you should know the right wire size for each job on the project. We give you some tips below.

Time needed: 5 minutes.


How to find the right wire size?

  1. Determine how much current you need


    This is crucial in finding the right wire size. If you pick a smaller size and the voltage is too much, your wire can melt and cause fires and accidents.

  2. Determine the length of wire you need


    Depending on the voltage and the area, you will need to calculate how long the wiring is. If the current that needs to flow is a lot, you will require longer wires. However, longer wires also cause more resistance and hence voltage drops.

  3. Determine gauge


    Due to all the above factors, it’s essential to work out the thickness of the wire required. If you’re going for especially longer wires, you’ll need a thicker wire to combat the resistance and voltage drops. Once you’ve figured out the length and current, you can easily check a table online. Match the amperage with the perfect gauge of the wire you require!

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