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

You may already know what a gauge is and how it works. If you don’t, we have a lot of valuable sections below on the topic to explore why you must choose the right product for your electrical needs. Scroll down if you want to look through NEC’s wire gauge amp chart table that we have included.

Summary: Buying recommendations through our wire size chart

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 an 8-gauge wire. For a 20 amp, you will need a 12-gauge wire. For 60 amp, the correct wire size is 4. The right wire size for 50 amp is a 6 for both your breaker & circuit. However, there are certain essential assumptions that that rule of thumb relies on. We will expand on those in the rest of this article.

The chart below will ensure you get the right extension cords and circuit breakers. Products were chosen based on the National Electric Code. A copy of the electrical wire sizing chart is included further down.

[rtbs name=”gauge-wire”]

Table of Contents

Simplified 20, 30, 40, 50, & 60 amp wire size chart

Scroll down to our full NEC wire size chart to find the corresponding options for different temperatures. The one below summarizes the main recommendations based on conductor temperatures of no more than 140°F.

Ground wire, service entrance, circuit, breaker size chart rating
Service or Feeder Rating, ampsAluminum conductor, AWGCopper conductor, AWG
20#1212
30#1010
40#68
50#46
60#34

60 amp

It can be confusing to understand what to install for this wire size as there are several different opinions on the internet. However, we suggest using AWG size 4 for a 60 amp wire size or breaker. You can also use AWG 3. Of course, when the wire length is longer, you can add a thickness of 10% for every 50 feet added.

Pros

  • We love that it’s 100′ long.
  • We even received marginally more than we ordered.
  • It works as intended.

Cons

  • You’ll need to use our table higher up to find other lengths.
  • No more complaints.

50 amp

AWG 6 wire is the perfect size for 50 amp circuits. You can opt for AWG 4 if the 50 amp breaker is connected to a wire longer than 100 feet or so. This generally features the most in air conditioner units, dryers, electrical furnaces, and water heaters.

Pros

  • You can choose between different lengths.
  • The longest length available is 200 feet.
  • It does what it’s supposed to.

Cons

  • Some buyers said they were sent shorter cables than they ordered.
WINDYNATION 
You can trust Windynation.

40 amp

AWG wire 8 is largely the recommended size for a 40 amp breaker. It’s generally installed for large devices like a stove, air conditioners, and water heating systems. Finding the right breaker size is crucial to protecting your wiring. Add 10% thickness to the wire for every 50 feet of wire added.

Pros

  • It arrived and works.
  • It was a good price for the purchase.
  • Heat resistant
  • Surprisingly flexible.

Cons

  • We have never heard of the brand before, but they delivered.
BNTECHGO 
You may not have heard of BNTECHGO before.

30 amp

A 30-amp circuit can take up many small appliances. As a rule of thumb, you can put up to 16 outlets on a single 30-amp circuit. Only use wire size AWG 8 for 30 amp draws to keep it intact. You can use appliances like a coffee maker, kettle, hair dryer, and more on these 30-amp circuits.

NameGS Power
Gauge10
Item Weight‎4.44 pounds
Length50 ft
Type99.9% Oxygen Free Copper Wire

Pros

  • It was great for the speakers we tried it with.
  • Great quality.
  • It was packaged nicely.

Cons

  • It arrived a bit later than expected.
Sale
GS Power 
It's a steal.

20 amp

AWG 12 is the perfect gauge of wire for a 20 amp breaker. You can expect it to safely carry up to 100 feet. You can size up to an AWG 10 copper wire if you plan on going longer than 100 feet. You’ll find these in kitchens and garages as they are used to power up big machines. It can power up your blender, microwave, stove, and coffee maker all on the same circuit as long as you use the right AWG.

NameBNTECHGO
Gauge12
Length50 ft
Number of Cable Strands680
TypeStranded Tinned Copper

Pros

  • Heat resistant
  • Very flexible
  • Easy to work with
  • Strong insulation

Cons

  • You may prefer stiffer wire.

AWG wire ampacity chart 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. They outline the values in slightly great detail than the previous charts did, as per the NEC 310.16 table. Scroll down further if you want a more detailed chart for the standard type.

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. A 12-gauge is the right wire size for your 220v 20 amp needs. Whether you’re finding out the option for your 1000 or 2000-watt needs, this is the chart the pros use. It can also be used for speakers and home theater. It’s commonly used for light fixtures or a subpanel. 

Whether for a 20, 30, 40, 50, or 60 amp circuit or breaker, the AWG wire size chart can help you find what you need. 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 Gauge167°F194°F140°F167°F194°F
14202025
122025252530
103035303540
84045405055
65060556575
46575708595
3758585100110
29010095115130
1100115110130145
1/0120135125150170
2/0135150145175195
3/0155175165200225
4/0180205195230260
250205230215255290
300230255240285320
350250280260310350
500310350320380430
600340385355420475
750385435400475535
1000445500455545615

The detailed chart further down in this article is for copper with an ambient temperature rating of 60 ℃ or 140 ℉. It is what is considered the standard. The suitable selection for a specific capacity will change depending on the wire used and the ambient temperature rating. If you want to find the 50 amp wire size at an ambient temperature of 194°F, you look in the chart to see gauge 6. Respectively for 40 amp, it’s gauge 8. The right 60 amp wire size 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. Copper or aluminum are the materials used for wires. The termination points and the ambient rating are other things you should be keeping in mind.

High ambient conditions like multiple conductors and the allowable voltage drop should be considered to ensure you don’t run into problems.

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

cord for lawn mower

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. The same thickness but with an ambient temperature rating of 90 ℃ or 194 ℉ can be safely used with a 25 amp breaker.

These factors make choosing the size for a 30 amp breaker not as straightforward as it seems. A 10 AWG copper with an ambient temperature rating of 60 ℃ or 140 ℉ is what you need from the chart above. You can also use an aluminum 10 AWG with a 90 ℃ or 194 ℉ ambient temperature rating and diameters larger than these two sizes.

It is fine to get a higher rating electrical component than the recommended one for a circuit breaker. Still, you should never use one with a lower breaker rating.

wires and subpanel

So, what exactly is the deal?

This is the measure of the diameter you will be using in different measurements. People will usually refer to the gauge rather than the actual thickness. The number refers to a specific thickness.

The higher the number, the smaller the diameter. It may be contrary to logic, but that’s how it is. The easiest way to determine the thickness of some wire you may have lying around is by using a thickness tool. Sometimes the rating is indicated. Sometimes it’s not.

You want to use the right diameter. The diameter determines the amount of current that can safely go through it, including the electrical resistance. Using the incorrect size could have serious consequences. Different amounts of current will require different diameters as well.

The unit of measure is AWG, the most popular measure in the US and is used in more than 65 countries. Other measures include the SWG and, the IEC, the Imperial Standard Wire Gauge. The British Board of Trade introduced it. Since most of our readers are from America, we will be focusing on AWG for this article.

As the diameter determines how much electricity can be carried, not all diameters work with every machine. You’ll also want to know about the cable length and voltage drop when you’re having a project done at your house. There are so many questions you need to be asking and knowledge you need, whether you’re installing water heaters or solar panel battery. It may even be for a generator!

Choosing the right one

When you inspect your circuit breaker, a burned wire 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 that this is something that many people do. People mistakenly believe that one wire is as good as any other. They attempt to make the connections themselves instead of calling for an electrician.

Anything involving breakers should be taken seriously because it has to do with electricity. It includes any sort of connectivity. You will avoid any electric hazards and issues common to circuit breakers and faulty connections if you have the right components. Many of these issues occur because of the wrong one being chosen and used for the breakers. It is important to know the right combination of the breaker and its compatible wires.

Maybe you are clueless about your 30 amp breaker size for an air conditioner or water heater. Allow us to help you understand the basics.

wire spool

What Happens if You Use One That Is Too Small?

People believe as long as both ends of a wire fit a connector. They can use it for their connections with no issue. Unfortunately, this is not the case for breakers. Those unaware of its importance often use too small wires to connect their breakers. They want to save money since thinner products tend to be cheaper. This is partly 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 is on your budget. This is because you spend more than you need to since larger wires cost more. It does not affect your breaker, nor will it cause damage to it. The wire can handle the current that flows through it.

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

  • Melting – the smaller the wire, the less current it can handle and the higher its resistance to energy flow. But if it is too small for your breaker and its rating, the current flows are more than what it is designed to handle. Since they have high resistance, heat is generated. This will eventually be enough to melt it if the power is too strong.
  • Performance Drops – any appliance or equipment 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 required 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. Circuit breakers can trip along with other safety measures. An overload has the potential to cause fires if the wrong one is used.

These scenarios are avoidable if you use the right type for a circuit breaker or air conditioner. You’ll also need to know the difference between copper wires and ones made of aluminum to have your electrical conduits working. It won’t just be an inconvenience if you don’t. It’ll be a disaster!

cord for outdoor use

Determining what breaker to use

Licensed electricians should ideally handle electrical work. It also helps to be personally aware of important aspects of your circuit breaker, such as having a good 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. It is commonly referred to as AWG. Also known as the Brown & Sharpe, the AWG is a system that prescribes specific diameters of solid round wires. You’ll hear the rating referred to as the gauge used as electric conductors. The capacity is the maximum current that it can safely handle.

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

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

AWGDiameter (inches)Diameter (millimeters)
00000.4611.68
0000.409610.4
000.36489.266
00.32498.251
10.28937.348
20.25766.544
30.22945.827
40.20435.189
50.18194.621
60.1624.115
70.14433.665
80.12853.264
90.11442.906
100.10192.588
110.090742.305
120.080812.053
130.071961.828
140.064081.628
150.057071.45
160.050821.291
170.045261.149
180.04031.024
190.035890.9116
200.031960.8118
210.028460.7229
220.025350.6438
230.022570.5733
240.02010.5106
250.01790.4547
260.015940.4049
270.01420.3606
280.012640.3211
290.011260.2859
300.010020.2546
310.008930.2268
320.007950.2019
330.007080.1798
340.006310.1601
350.005620.1426
360.0050.127
370.004450.1131
380.003970.1007
390.003530.08969
400.003140.07986

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

BNTECHGO
You may not have heard of BNTECHGO before.

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 ℉.
cord

Before we get into the basics of reading a wire size chart, let’s see what factors affect the gauge. How much current it can carry will depend on various factors like the thickness and material. Sheathing and insulation play a role as well. Now let’s look at the steps needed to read wire size charts:

How much does it take to handle 25 and 35 amps?

The rule of thumb is that you at least need a 12 gauge wire for a 20 amp service. You could use an AWG 10 but not a 14-rated one. We still encourage you to refer to the detailed NEC table above to decide which to go for.

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.

wire outside

A 10 AWG copper with either a 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉ ambient temperature rating can handle 35 amps. The equivalent aluminum one with an ambient temperature rating of 90 ℃ or 194 ℉ can also work.

If you wonder if your extra 12 AWG can also be used for a 25 amp breaker, it is. In copper, it can be used if its ambient temperature rating is either 75 ℃ or 167 ℉ or 90 ℃ or 194 ℉. The equivalent aluminum one is compatible if its ambient temperature rating is 90 ℃ or 194 ℉.

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

Safety measures to follow with electrical work

Dealing with electric repair work should always be left to a professional. Maybe you’re a beginner in that field. Here are some tips you should always keep in mind when dealing with industrial or commercial breakers.

look inside a subpanel
  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 must be appropriately informed and trained to deal with hazardous energy sources.
  • Notify the affected personnel. All persons on site affected by the shutdown/ lockout must be notified of its timing and reasons.
  • Shut off equipment. All manual operating procedures must be done to shut off the running equipment in a timely and safe manner.
  • Isolate the power origins and sources. It will mean any valves supplying power to the equipment and machinery must be cut off temporarily.
  • Lock out all power sources. It can mean through a physical padlock so that no one can access or physically turn on the equipment during the shutdown time.
  • Release the stored power. Some machinery holds air or energy or electric charge which must be released.
  • Double-check the LOTO process. It means ensuring all the steps above have been followed and checked off the checklist.
  • Control the LOTO. Appropriate personnel must be appointed to overlook and ensure the shutdown is in place. It’s all the while the maintenance work is being done.

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

  1. Wearing safety clothing

Electricians must always wear safety gear when working with circuit breakers or any electrical equipment. It includes personal protective equipment like PPE suits and safety goggles.

  1. Make sure all the constituents match with each other

Match the wiring with the appliances and the switchboards and ensure it aligns with the load requirements.

  1. Watch your hands!

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

  1. Take count of your tools.

The tools, wires, and other fittings must be thoroughly counted before and after maintenance. This ensures that no damaged parts are being used in the installation. Counting the tools will ensure nothing is left inside the control panel and switchgear 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. It can keep your whole factory or workplace running smoothly.

  1. Meet code requirements

When any new electrical parts are installed, it’s essential to check whether you meet local electrical code standards. National Electrical Manufacturers Association (NEMA) or Institute of Electrical and Electronics Engineers (IEEE) guidelines are great. They have control procedures to 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. Under no circumstances should an employee be allowed to handle the electrical panels. Handling electricity and current can prove dangerous. 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 fire or electric hazards. It’s always better to stock up on prevention measures than regret later!

outside wires

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