20, 30, 40, 50 & 60 Amp Wires, Breakers & Circuits Chart: What AWG Size Do I Need For My Project?

You may already know what a gauge is and how it works, but in case you don’t, we have a bunch of useful sections below on the topic to further explore why it’s crucial you choose the right product. Scroll down if you want to look through NEC’s wire gauge amp chart table that we have included.

In a hurry? Buying recommendations

We spent more than 20 hours screening manufacturers and reviews to come up with this list of products to ensure that your extension cords, circuit breakers or service wire can handle the electrical current you’ll be running through it. They were chosen on the basis of the National Electric Code (the safety standard used by pros – a copy of the electrical wire sizing chart included further down).

Table of content

A Rule of Thumb: What are the correct wire sizes for 20, 30, 40, 50 & 60 Amp Service & Breakers?

What wire do I need for various capacity requirements? The rule of thumb that techs will usually go by is that for a 30 amp circuit breaker, 10-gauge wire is the right one to go with. For a 40 amp you need a 8-gauge wire. For a 20 amp, you will need a 12-gauge wire. For 60 amp, the right wire size is 4, however there are certain important assumptions that that rule of thumb relies on – we will expand on those in the rest of this article. The right wire size for 50 amp is a 6, for both your breaker & circuit.

When you start comparing with the chart below, you will see that those numbers are on the conservative side, however, it’s better to get a safer option, even if it may be marginally more expensive. To find the corresponding options for different temperatures, scroll down to our full NEC wire size chart. The one below simply summarizes the main recommendations on the basis of conductor temperatures of no more than 140°F.

Ground wire, service entrance, circuit, breaker size chart rating

Service or Feeder Rating, amps Aluminum conductor, AWG Copper conductor, AWG
20 #12 12
30 #10 10
40 #6 8
50 #4 6
60 #3 4

AWG wire ampacity chart & gauge rating from NEC 310.16

Looking for the NEC (National Electric Code) wire ampacity chart and size rating tables across the internet, these are the values that we have been able to find which outlines the values in slightly great detail than the previous charts did, as per the NEC 310.16 table. If you want a simpler chart for the standard type, scroll down further, where we have taken the most conservative numbers to ensure your safety.

As you can see from the graph, a 6 AWG is the safe choice if you have a 220v 50 amp that you need to power, whereas a 12 gauge wire is perfect for your 220v 20 amp needs. Whether you’re finding out the right option for your 1000 or 2000 watt needs, your speakers, your home theater, your subwoofer, your light fixtures, your light bar or your sub panel, this is also the chart that the pros use. 

Whether it is for a 20, 30, 40, 50 or 60 amp circuit or breaker, the AWG wire size chart below can help you find the right one to go with. It is the most accurate table to go with on this page and is the one that the pros use. 

  Aluminum, Amp Rating     Copper, Amp Rating  
Wire Gauge 167°F 194°F 140°F 167°F 194°F
14 20 20 25
12 20 25 25 25 30
10 30 35 30 35 40
8 40 45 40 50 55
6 50 60 55 65 75
4 65 75 70 85 95
3 75 85 85 100 110
2 90 100 95 115 130
1 100 115 110 130 145
1/0 120 135 125 150 170
2/0 135 150 145 175 195
3/0 155 175 165 200 225
4/0 180 205 195 230 260
250 205 230 215 255 290
300 230 255 240 285 320
350 250 280 260 310 350
500 310 350 320 380 430
600 340 385 355 420 475
750 385 435 400 475 535
1000 445 500 455 545 615

The simpler chart further down in this article is for copper with an ambient temperature rating of 60 ℃ or 140 ℉, which is considered as the standard. But in some cases, the suitable selection for a specific capacity will change depending on the wire used and the ambient temperature rating, as you can see from the detailed table above. Assuming you want to find the 50 amp wire size at an ambient temperature of 194°F, you simply go up and look in the chart to see it’s gauge 6. Respectively for 40 amp, it’s gauge 8. For 60 amp, the right wire is gauge 4 at an ambient temperature of 140°F. These numbers are assuming you’re going for aluminum. 

In those situations, it’s important to think about what the conductor is made of, and whether it is in fact copper or something else like aluminum. Other things like the type of load and the ambient rating as well as its termination points are other things you should be keeping in mind, as the above is only a rule of thumb.

High ambient conditions like multiple conductors as well as the allowable voltage drop should be considered so as to make sure you don’t run into any problems.

Copper is known to be able to carry more electricity than aluminum, that is why at the same gauge, it can handle more compared to its aluminum counterpart. This means if you have a copper 6 AWG and the same made of aluminum, the copper will allow more current to flow through it.

Not only that, but electrical components with a higher ambient temperature rating can be used at higher current requirements. This is why a copper 14 AWG wire size with a 60 ℃ or 140 ℉ ambient temperature rating is suitable for a 15 amp breaker, while the same thickness but with an ambient temperature rating of 90 ℃ or 194 ℉ can be safely used with a 25 amp breaker.

These factors are what makes choosing the size to use for a 30 amp breaker not as straightforward as it seems. From the chart above, a copper 10 AWG copper with an ambient temperature rating of 60 ℃ or 140 ℉ is seen as standard in most conditions. However, you can also use an aluminum 10 AWG with a 90 ℃ or 194 ℉ ambient temperature rating, as well as diameters larger than these two sizes.

Always remember that it is fine to get a higher rating electrical component than the recommended one for a circuit breaker, but you should never use one that has a lower rating of the breaker.

circuit breaker

So, what exactly is the deal?

This is basically the measure of the diameter that you will be using and it comes in different measurements. People will usually refer to 12, 10, 14, 8 and 6 gauge rather than referring to the actual thickness of it, where one number refers to a specific thickness.

Contrary to logic belief, the higher the number, the smaller the diameter, and the easiest way to determine the thickness of some wire you may have lying around is by using a thickness tool, in case it is not clearly indicated on it already which thickness you are dealing with.

The reason you will want to make sure that you are using the right diameter is because the diameter determines the amount of current that can safely go through it, including the electrical resistance, and using the incorrect size could have serious consequences, why different amounts of current will require different diameters as well.

The unit of measure is AWG, which is the most popular measure in the US and is in fact used in more than 65 different countries. Other measures include the SWG and the IEC, the latter being the Imperial Standard Wire Gauge, which was introduced by the British Board of Trade. For this article, since most of our readers are from America, we will be focusing on AWG.

As the diameter of these determine how much electricity can safely be carried through them, it is obvious that not all diameters fulfill the purpose for every single machine.

Choosing the right one

A burned wire when you inspect your circuit breaker is a surprise that you do not want to get. Fortunately, this is an avoidable scenario if you know that having the right capacity for a circuit breaker is important. The bad news is, this is something that a lot of people; they mistakenly believe that one wire is as good as any other so they attempt to make the connections themselves instead of calling for an electrician.

Anything involving breakers, such as its connections, should be taken seriously because it has to do with electricity. If you have the right components installed, you will avoid any known electric hazards and issues common to circuit breakers and faulty connections. In fact, many of these issues occur because of the wrong one being chosen and used for the breakers. This is why it is important to know the right combination of the breaker and its compatible wires.

If you have a 30 amp breaker right for your air conditioner, water heater, or clothes dryer that needs to be installed but you are clueless about what size is needed, allow us to help you out with not just that but also in understanding the basics.

Incorrect wire size and amp rating causing burning wire

What Happens if You Use One That Is Too Small?

People believe that as long as both ends of a certain wire will fit a connector, they can use it for their connections with no issue. Unfortunately, this is not the case for breakers. Those who are unaware of its importance often use too small wires to connect their breakers, often because they want to save money since thinner products tend to be cheaper, in part because less material is used.

Sadly, this only leads to costly mistakes for them.

If you use larger ones on your breaker, the only effect it will have is on your budget. This is because you ended up spending more than what you need to since larger wires cause more. It does not have an effect on your breaker nor will it cause damage to it, as it can handle the current that flows through it.

But if you use one that is too small, the following can happen:

  • Melting – the smaller it is, the less amount of current it can handle and the higher its resistance to the flow of energy. But if it is too small for your breaker and its rating, the current that flows is more than what it is designed to handle. Since they have a high resistance, heat is generated and this will eventually be enough to melt it if the power is too strong.
  • Performance Drops – any appliance or equipment that is connected to the circuit with the too-small wire will not operate at peak efficiency. This is because it receives only a fraction of the energy it requires to run at full performance.
  • May Damage Equipment – aside from affecting its performance, using a smaller diameter can eventually damage your equipment. Power being supplied improperly can cause them to go bust
  • Can Start Fires – this is the worst that can happen when it is too small to handle the current it receives. While circuit breakers have their own safety measures, such as tripping when it experiences an overload, this may not be enough to prevent a fire because of the wrong one being used.

These scenarios are totally avoidable, as long as you use the right type for a circuit breaker.

Determining what breaker to use

While electrical work should ideally be handled by licensed electricians, it also helps to be personally aware of important aspects of your circuit breaker, such as the one having the right rating for the project. To select the right one, professionals use different charts as their reference.

In the USA, the chart that is considered standard is the American Wire Gauge, commonly referred to as AWG. Also known as the Brown & Sharpe, the AWG is a system that prescribes specific diameters of solid round wires, referred to as the gauge, to be used as electric conductors. The capacity is the maximum current that it can safely handle.

What you should note is that the AWG numbering system does not directly represent the actual size. This means the higher the AWG number, the thinner or smaller it is, the less power it is rated to handle. This is why a 2 AWG can carry more current than a 14-rated one.

To better understand it, you can use the following chart to determine the diameter in inches and millimeters in terms of the AWG number. Whether you’re looking for 20, 30, 40 or 50 amp wire sizes, the chart below should help you out:

AWG Diameter (inches) Diameter (millimeters)
0000 0.46 11.68
000 0.4096 10.4
00 0.3648 9.266
0 0.3249 8.251
1 0.2893 7.348
2 0.2576 6.544
3 0.2294 5.827
4 0.2043 5.189
5 0.1819 4.621
6 0.162 4.115
7 0.1443 3.665
8 0.1285 3.264
9 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

As you can see, the largest in terms of diameter is 0000, while the smallest is 40. This means the 0000 has a bigger capacity than one that has a 40-rating, and this also means that the 0000 allows more energy to flow through it.

Circuit Breakers

What is a circuit breaker?

This is the safety switch that automatically interrupts electrical current when it senses an overload or short. It shuts down or ‘breaks’ the electrical flow of current so as to protect the rest of the electrical equipment and wiring from an electrical fire. Therefore, it is absolutely essential to have a good and compatible breaker installed in your home, workplace or factory.

What are the different types?

There are three main types used in electrical circuits – standard, GFCI and AFCI. Let’s look at them in more detail below:

Standard breaker

These are called standard for a reason. They are of the simplest type and monitor the flow of current indoors. It’s job is to keep track of the current flowing through devices, wires and outlets. Whenever the device senses an overload or a short coming, it stops the current entirely to prevent the wires from melting and prevent accidents like fires from happening.

A Ground Fault Circuit Interrupter

This type is more complex and has more useful functions as well. A GFCI includes an outlet with a breaker built in. But the most important function it provides is that of protection against electrical fires due to contact with water. For this reason, a GFCI is installed in kitchens, bathrooms and other areas with frequent use of water.

For instance if you’re using a blender in the kitchen and the circuit overflows with electricity because it comes in contact with water, the breaker inside the outlet will trip and immediately stop all current from flowing to prevent any hazards. If something like this happens in your home, you should get the outlet checked by a professional before using it again.

Arc-Fault Circuit Interrupter

These are specialized devices designed to interrupt the flow of current when they sense an arc or surge in the electrical flow due to damaged or worn out wiring. This kind of surge goes undetected in other standard breakers since they react to heat and not sudden surges of electric discharge.

The latest National Electric Code guidelines makes it compulsory to have GFCI and AFCI breakers in the kitchen and laundry rooms, since this is the place where electric fires are more likely to happen. However, you can choose to install AFCI breakers in living room, bedrooms, libraries, closets and hallways too.

Combination arc-fault circuit interrupter

These are ones with the combined power of both GFCI and AFCI protection. Not only do they sense any arcing due to damaged wiring, but also water contact. They can protect against both arc and ground faults. Installing CAFCI breakers can save you more on money and fetch your one-time long lasting protection for your home.

Make sure to test the GFCI and AFCI devices every month to see that they are in good working condition. You can also schedule a servicing every few months and get your electrical panels checked thoroughly.

Now that you have a better understanding of the relationship between the various parts of the equation, it is time to determine which is suitable. You may not necessarily be a licensed electrician, but you still know some of the things you should be aware of when it comes to ensuring the safety in your home, at least when you’re dealing with electricity. 

If you have no idea where to find the rating, look for the number on the handle of the breaker itself; this number is the maximum capacity it can handle.

Once you find the rating, you can now determine which electrical components are the right ones for you to use. The most common ones and their corresponding ratings are:

Wire Gauge (AWG Number) Ampacity
14 15
12 20
10 30
8 40
6 55
4 70
3 85
2 95

How Many Amps Can a 12 AWG Handle?

The amps that a 12 AWG can handle are:

  • 20 for copper with an ambient temperature rating of 60 ℃ or 140 ℉, which is the most common connection
  • 25 for copper with an ambient temperature rating of 75 ℃ or 167 ℉
  • 30 for copper with an ambient temperature rating of 90 ℃ or 194 ℉
  • 20 for aluminum with an ambient temperature rating of 75 ℃ or 167 ℉
  • 30 for aluminum with an ambient temperature rating of 90 ℃ or 194 ℉

How much does it take to handle 20, 25 & 30, 35 amp?

The rule of thumb is that you at least need a 12 gauge wire for 20 amp service, why you would be able to use a 10, but not a 14-rated one. We still encourage you to refer to the detailed NEC table that we have included above when you are deciding which to go with.

Say you have a 35 amps breaker and a 10-gauge wire lying around. You may be wondering if this particular one can handle that much current. It is possible but it will depend on the type of material and its ambient rating.

A 10 AWG copper with either a 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉ ambient temperature rating, as well the equivalent aluminum one with an ambient temperature rating of 90 ℃ or 194 ℉ can handle 35 Amps.

If you are wondering if your extra 12 AWG can also be used for a 25 amp breaker, it is possible to do so. In copper, it can be used if its ambient temperature rating is either 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉, while the equivalent aluminum one is compatible if its ambient temperature rating is 90 ℃ or 194 ℉.

How much does it take to handle 50 amps?

If you looked at our chart above, you can see this amount of power hasn’t in fact been included in it, but we’re still finding that there are a lot of people out there asking the question of what the appropriate diameter is for this amount of power. The truth is that 8, 10 or 12 gauge can’t handle it. The 50 amp wire size is gauge 6 in this instance, given the same conditions that we stated earlier in the article. On the other hand, you need a wire size 4 for 60 amp service, sub panel or breaker.

How much does it take to handle 30 amps?

To answer this question, it’s important that you consider the same conditions that we previously noted with regards to ambient temperatures. Yes, you can use a 10 AWG size wire for 30 amps, but you can’t use a 12 or 14 AWG for this amount of power as it simply cannot handle it. In fact, consider a 10/3 cable for 220-volt outlets, which is a great residential option for a power circuit of this strength. This type has a ground wire as well as 3 live ones.

On the other hand, when you are having to power something like light switches, you will want a 10/2 wire instead, which is made for that purpose. The second number refers to the number of live wires, although it also contains one for ground purposes. Because there is a distinction between the two, it is important that you know what exactly it is you’re planning on powering, so that you can make sure to get the right electrical components for the purpose.

So, next time you’re working on wiring a 30 amp double pole breaker, you can refer to this guide to make sure you’re not making one of the crucial mistakes that could unfortunately lead to severe consequences. On the other hand, if you are trying to hook up something larger, like a double oven, for instance as well as a high-end stove, you’re likely looking at a 6/3 or 8/3 option instead, as these are rated for higher consumption than the 10/3 is.

How much does it take to handle 40 amps?

As you can see from our rule of thumb section, you will need a 8 gauge wire for 40 amps, why a 10 AWG will not be able to handle this amount.

electrician installing 30, 40, 50, 60, 100, 200 amp wire

How to install a circuit breaker?

Now that we’ve gotten you familiar with circuit breakers and gauges, let’s take a look at how to install a circuit breaker if you decide to go DIY. Remember, only perform this under the supervision of a licensed electrician until you learn to do it yourself.

    1. Turn off the main power

There should be no current in any wires in the panel. Turn off the main power and then open up the panel of the breaker. Main breaker wires will still be live so it’s important to test them and make sure no current is flowing for safety purposes. Once this is done, you can begin the process.

    1. Screw on the cable clamp

You’re going to need a new cable clamp if you want to install a new breaker. For this, use a hammer on the knockout and make room for the new cable clamp. Find the new wire and run it through the panel and to the clamp.

    1. Install the ground wire

Affix the ground wire into the ground bar. This should be done with care since this is the only one that has no insulation and thus carries more safety risks.

    1. Connect the neutral wire

Next, the neutral wire must be connected to the neutral bus. This can be done easily if you simply remove a little bit of insulation around the end of the wire. Feed this tip into the bus and tighten it.

    1. Circuit breaker installation

Look for a screw on the bottom of the breaker. Affix the last black wire under this screw. When this is done, tighten the screw and hold it steadily. There are prongs on the back which you can use to align it in the correct manner.

    1. Take out the knockouts

Now you can safely place the knockouts over the newly installed circuit breaker. This will ensure that they are shielded carefully.

Safety measures to follow with all types

Dealing with electric repair work should always be left to a professional. However, if you’re a beginner in that field, here’s some tips you should always keep in mind when dealing with industrial or commercial breakers.

  1. Never forget to shut off the main breaker

Here it’s useful to follow the Lockout/ Tagout procedure or LOTO protocol. The LOTO protocol involves the following eight safety steps:

  • Good preparedness and training – Everyone affected by the shutdown including employees and other workers on the site must be appropriately informed and trained to deal with the hazardous energy sources.

  • Notifying affected personnel – All persons on site who will be affected by the shutdown/ lockout must be notified of its timing and reasons well in advance.

  • Shutting off equipment – All operating manual procedures must be done to shut off the running equipment in a timely and safe manner.

  • Isolate the power origins and sources – This will mean any valves that are supplying power to the equipment and machinery must be cut off temporarily.

  • Lock out all power sources – this can mean through a physical padlock or other tools so that no one can access or physically turn on the equipment during the shutdown time.

  • Release the stored power – Some machinery hold air or energy or electric charge which must be released.

  • Double check the LOTO process – This means ensuring all the steps above have been followed and checking off the checklist.

  • Control the LOTO – Appropriate personnel must be appointed to overlook and ensure the shutdown is in place all the while the maintenance work is being done.

Following this LOTO protocol isn’t just part of dealing with circuit breakers but is a common practice followed in major electrical maintenance work in any factory unit or industrial area.

  1. Wearing safety clothing

When working with circuit breakers or any electrical equipment, electricians must always wear safety gear. This includes personal protective equipment like PPE suits and safety goggles if you’re work requires some welding.

  1. Make sure all the constituents match with each other

Match the wiring with the appliances and the switchboards and ensure it is in line with the load requirements.

  1. Watch your hands!

Remember, even though the power may be off, the main bus bar and other parts may still be hot to the touch. Ensure sufficient time between shut down and handling for the bus bar to cool off. Even the conductors could have leftover electrical charge and therefore must only be handled after proper isolation procedures have been followed.

  1. Take count of your tools

The tools, wires and other fittings must be thoroughly counted before and after the maintenance work. This ensures that no damaged parts are being used in the installation. Also, counting of the tools will ensure nothing is left inside the control panel and switch gear during the maintenance work.

  1. Maintenance

Your circuit breaker should be routinely serviced to maintain its long life and ensure its proper working. You can take advantage of yearly servicing packages and ensure that your system gets enough attention and care to keep your whole factory or workplace running smoothly.

  1. Meet code requirements

Especially when any new electrical parts are installed, it’s essential to check up on whether you’re meeting the local electrical code standards and guidelines. National Electrical Manufacturers Association (NEMA) or Institute of Electrical and Electronic Engineers (IEEE) guidelines and control procedures will help you set electrical maintenance standards in your workplace.

  1. Only the right person for the job

We cannot stress this one enough. Make sure you hire a skilled and experienced technician or electrician for the job. Under no circumstances should an employee be allowed to handle the electrical panels. Handling electricity and current can prove dangerous and thus all the safety precautions above must be read and followed carefully.

Following these tips can provide you and your family or co-workers with long-lasting protection against any fire or electric hazards. It’s always better to stock up on prevention measures than to regret later!

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