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

Suppose one uses the incorrect wire for the circuit breakers. In that case, there is a considerable probability that the wire will melt.

If the wire conducts a current that is greater than its capacity it has, then the wire will get heated.

This results in the wire melting, and in the worst-case scenario, it may cause a fire hazard. After a look at this article, you will easily be able to tell the gauge of the wire for 30 amp.

What is Wire Gauge?

Before we delve into different gauge wires for 30 AMP, we need to know what a wire gauge is. You might have seen the abbreviation AWG being used here and there.

It stands for American Wire Gauge, and it tells us about the size of the wire and how much current it can safely handle. A higher gauge number means that the diameter of the wire is a smaller one.

That means as the gauge number goes up, the resistance per unit length of the wire also increases. This, in turn, points that the amount of current that the wire can handle is decreased. Here is a chart to help you get a better idea about it,

AWGDiameter (inches)Resistance (Ohms per 1000ft)Ampacity (amp)

Why Different Size for Different Ampacity?

If you ever went out and got some wire on your own, you must have noticed that there are quite a few sizes to choose from. The versatility is mainly caused due to their usage. Same wires can not be used for all things.

For example, if you were to use a fuse or circuit breaker wire as the power cord for your table fan, then it is sure to cause a fire hazard.

This is why it is recommended to learn about the wire size or gauge before purchasing them. It helps you make the correct choice. To learn about the size, you need to know the American Wire Gauge (AWG) system.

Wire gauge tells you about the diameter and also the resistance per unit length. Using these data, one can easily get an idea about what amount of current can be safely conducted by the wire. So, this results in different ampacity for different sized cables.

Here is a table of amperage capacity for standard non-metallic cable or wire,

Wire Size or GaugeAmperage capacity
14-gauge wire15 amps
12-gauge wire20 amps
10-gauge wire30 amps
8-gauge wire40 amps
6-gauge wire55 amps
4-gauge wire70 amps
3-gauge wire85 amps
2-gauge wire95 amps

Seeing the chart, it is evident that the wire size matters. Unless you don’t mind setting your house or workplace on fire, that is. Without the correct size wire, you won’t be able to get the predicted result.

Rule of Thumb for Service and Breaker Wires

Now that you have a vague idea about the relation between different wire gauge and their amperage capacity, a new question pops up. What gauge wire do you need?  There is a rule of thumb that technicians generally follow.

This rule of thumb relies on a few assumptions, which will help you get a clear idea about what gauge wire could be appropriate for you. For example, based on the rule of thumb, 10-gauge wire is best for a 30 amp circuit breaker.

But for a 40 amp circuit breaker, it is perfect to go with an 8-gauge wire size. On the other side, 12-gauge wire size can handle 20 amp current, and for a 60 amp, you will need a wire gauge size 4. However, there are apparent crucial assumptions – we will try to cover all of those to help you make a fair deal.

In reality, the amperage capacity of a wire depends not only on the gauge of the wire. It is also dependent on the material of the wire. We know that different materials have different conductivity. This is a significant factor when it comes to wires.

For instance, a 4-gauge copper wire can have the same amperage as a 3-gauge aluminum wire. On the other hand, a 6-gauge aluminum wire will give 40 amp, but a copper 6 gauge wire has 50 amp amperage capacity.

The temperature that they operate in is also a factor in calculating the gauge requirement. That is why it is better to get the perfect gauge wire, even if it means that one would have to pay a bit more. Safety of life is the main thing.

This is why we humans made circuit breakers and service wires. If one isn’t safe, then what even are these breakers useful for. That is why it is advisable to get the gauge wire that would be perfect for the job.

AWG vs. Ampacity Chart and Gauge Rating from NEC 310-16

If one wants to get the perfect wire for their project or even their residence, they need to look at the NEC chart.

NEC or National Electric Code is a benchmark for safe and electric design, installation, and inspection. All 50 states already adopted the measure. They have proposed wire ampacity chart and gauge rating tables.

This chart categorizes the size and amp relation with further details than the previous charts. The latest data chart is the NEC 310-16.

No matter the purpose, you can cross-reference the chart to find the perfect gauge wire, even for 20, 30-, 40-, 50- or 60-amp circuit or breaker. Take a look at the chart.

Wire Gauge SizeAmpacity of Copper Wire
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
1420 (15)20 (15)25
12 25 (20)25 (20)30
10 3035 (30)40
Wire Gauge SizeAmpacity of Aluminum Wire
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
12 20 (1)20 (1)25 (1)
10 2530 (1)35 (1)

As you can see in the chart, different gauge wire has different amperage capacity at different temperature. But for a specific ampacity, the suitable wire gauge will also change depending on the ambient temperature.

NEC also provides another chart considering this. The first chart values are based on the ambient temperature being 30° C or 86° F. So if the ambient temperature is higher than this, what to do? Well, simply multiply the values of the first chart with the values from the second chart.

The second chart is as follows,

Ambient TemperatureFor Copper
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
21-25 °C, 70-77 °F1.081.051.04
26-30 °C, 78-86 °F111
31-35 °C, 87-95 °F0.910.940.96
36-40 °C, 96-104 °F0.820.880.91
41-45 °C, 105-113 °F0.710.820.87
46-50 °C, 114-122 °F0.580.750.82
51-55 °C,123-131 °F0.410.670.76
56-60 °C, 132-140 °F0.580.71
61-70 °C, 141-158 °F0.330.58
71-80 °C, 159-176 °F0.41
Ambient TemperatureFor Aluminum
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
21-25 °C, 70-77 °F1.081.051.04
26-30 °C, 78-86 °F111
31-35 °C, 87-95 °F0.910.940.96
36-40 °C, 96-104 °F0.820.880.91
41-45 °C, 105-113 °F0.710.820.87
46-50 °C, 114-122 °F0.580.750.82
51-55 °C,123-131 °F0.410.670.76
56-60 °C, 132-140 °F0.580.71
61-70 °C, 141-158 °F0.330.58
71-80 °C, 159-176 °F0.41

As you can see, the ambient temperature multiplier for both types of wire is the same. But if you look at the first chart, you will see that multiple gauge wire can provide the same ampacity at different temperatures.

Get the Perfect Gauge

The gauge of a wire determines what the diameter of a wire would be. We know that the more the diameter, the less the resistance per length. And the lesser the resistance per length, the greater the ampacity. So, the gauge is actually related to the ampacity of the wire.

But you might have heard a myth regarding the gauge of wire.

The myth goes that a wire can be used anywhere where electricity needs to pass regardless of the wire gauge. This myth is entirely baseless. Whey we say that just take a look at the chart below,

Wire GaugeDiameter (inch)Diameter (mm)Ampacity of Copper at 90 °C (194 °F)

This shows that ampacity indeed does depend on gauge wire. Other than this, there is one major reason to which the wire gauge needs to be perfect.

If the wire used in any project is not perfect, it will struggle to conduct the required current. This will result in the wire getting fried or commonly known as burnt. Which is highly fire hazardous. So, if you don’t want to ruin your project, then get the perfect gauge wire.

What is the Correct Size?

The gauge of a wire is related to the diameter, and the diameter, in turn, is connected to ampacity. Thus, without a doubt, the ampacity or amperage capacity of the wire is dependent on the wire gauge or wire size. Now the question is, how are they related?

From common sense, one would think the higher the wire gauge, the better the ampacity. But that is not the case here. As the gauge increases, the diameter or cross-section of the wire is decreased. Here is a chart to help you understand,

AWGDiameter (inch)Cross-Sectional Area (sq. in.)Diameter (mm)Cross-Sectional Area (sq. mm)

Relation Between Wire Gauge and Circuit Breaker

After reading so far, it would not be wrong to say that you have already understood that wire gauge is inversely related to a wire’s ampacity.

So, you might be thinking of utilizing this knowledge, but you don’t know-how. Well, you don’t need to worry about it.

This is because there are things like circuit breakers to assist you in this case.

The only thing you need to know is which ampacity is given by what gauge or AWG. Here is a brief chart of the essential daily utensils and their probable ampacity and gauge,

Probable UsageEstimated Ampacity (amp)Recommended AWG
Low-voltage lighting and lamp cords1018
Light-duty extension cords1316
Light fixtures and lighting circuits1514
Indoor and outdoor receptacles2012
Electric clothes dryers and water heaters3010
Cooktops and ranges40-506
Electric furnaces, large electric heaters604

The chart doesn’t have all the electric appliances a house may have. But seeing the chart, you can get an estimated idea about the required gauge.

This will help you preserve the circuit breakers that the devices already have. For example, if the gauge is smaller than the recommended, then the ampacity supply will increase.

This will result in the circuit breakers supplying higher ampere and melt or, worse, catch fire. On the other hand, if the wire gauge is greater, then a lowers supply of power will damage the device internally.

That is why it is crucial to know the relation between the required gauge and circuit breakers.

What if the Wire Gauge is Bigger?

Many believe that as long as both ends connect, any wire is ok for the job. But that is not the case if one is thinking of using these wires as breakers. If one is unaware of the fact, they will fail and might cause a massive accident.

As you have seen, a smaller gauge is higher ampacity, and the reverse is valid for a bigger gauge. That means the higher the gauge, the smaller the diameter and ampacity.

If one uses a higher gauge wire instead of the recommended one, there would be quite a few problems. If the wire size is small and a current of higher amperage passes through, the wire would melt. That is the basic principle for breakers.

But what if the capacity of the wire is lower than the required? Then the wire would melt even before the required power is passed. This will result in the device being completely unusable.

Even if the necessary current passes, due to the smaller size, the wire will get superheated. This may cause fire and damage not only the device but also the surroundings.

Let us consider for some miraculous reason the wire doesn’t melt. Then the device will work, but it will have lower power than required. This will damage the amplifiers within the device.

That is because the amplifiers will have to work overtime to keep the device running. So repeated use in this state will lower the efficiency of the device.

What if the Wire Gauge is Smaller?

If the wire used in a breaker has a smaller gauge than the required, the breaker will malfunction. If such happens, then the safety one expects from the breaker will not be effective.

That is because if a wire of a smaller gauge is used, then the size is larger than the required, and if the size is smaller, the ampacity is also higher. This is why it is advisable not to use a wire whose gauge is smaller than required. If one does so, the wire will have a higher ampacity.

If the wire’s ampacity is greater, then the breaker will allow more current flow than recommended. If this happens, the device or project that the breaker is supposed to protect will get overcharged. This will burn the delicate internal circuits that the breaker was supposed to prevent.

For example, there is an amperage capacity for some speakers. This capacity is supposed to be safeguarded by breakers.

But if the breaker allows more current to flow than recommended, then the speaker’s delicate circuits will be damaged. In the worst-case scenario, the circuits will burn or melt, destroying them beyond repair.

This is just an example of a simple speaker. If the circuit breaker of the mainline for your house’s electricity fails, then the damage is far more disastrous. All the electric devices that would be subjected to this high ampere surge are sure to be damaged and cost you a fortune.

Which Breakers to Use?

If you are not a licensed electrician, it is better not to handle electric circuits. This is because, without proper training, you are sure to do something wrong and cause disaster.

But there is one thing that you need to know even if you are not a licensed electrician. This is the importance of circuit breakers. Not just their importance, it is also recommended to learn about their required wire gauge.

There is the NEC chart in the states that helps one get an in-depth idea about the required size or AWG for required ampacity.

But for a general civilian, the chart may seem a bit too complex. That is why here is a simplified chart. This chart will help you identify the required gauge for accepted ampacity. So using this, you can select the perfect breaker that you need.

Required AmpacityRecommended AWG

Wire Gauge for 30 amp

So far, we have seen a lot of charts. They all had information regarding the various AWG for different ampacity. For example, the NEC 310-16 chart has all the possible ampacity for all possible wire gauges. But the focus of this article is to get an idea about the correct size for 30 amp.

Now, if we talk about the perfect gauge wire for 30 amp, there are many possible answers. This is because the ampacity of a wire depends not only on the wire’s gauge or diameter.

It is a subject that varies due to material and temperature. It is also dependent on the ambient temperature. Here is a brief chart that shows the different gauge requirements for different materials for an ampacity of 30 amp.

Ambient TemperatureCopper Wire Gauge at Different Temperatures
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
21-25 °C, 70-77 °F
26-30 °C, 78-86 °F1012
31-35 °C, 87-95 °F
36-40 °C, 96-104 °F10
41-45 °C, 105-113 °F810
46-50 °C, 114-122 °F6
51-55 °C,123-131 °F410
56-60 °C, 132-140 °F8
61-70 °C, 141-158 °F8
71-80 °C, 159-176 °F6
Ambient TemperatureAluminum Wire Gauge at Different Temperatures
60 °C (140 °F)75 °C (167 °F)90 °C (194 °F)
21-25 °C, 70-77 °F10
26-30 °C, 78-86 °F810
31-35 °C, 87-95 °F10
36-40 °C, 96-104 °F10
41-45 °C, 105-113 °F610
46-50 °C, 114-122 °F4810
51-55 °C,123-131 °F2
56-60 °C, 132-140 °F68
61-70 °C, 141-158 °F2
71-80 °C, 159-176 °F4

Frequently Asked Question (FAQs)

1. How many amps can 10 gauge wire handle?

Each wire gauge has an optimum current holding capacity. This measurement lets you learn how much current a wire can handle safely. Most individuals need 10 gauge wire for different installation projects.

Now the question arises, how many amps can 10 AWG handle. So, if you want to go with the thumb role, 10 gauge wire may carry a maximum of 30 amps. That is to say, any circuit breaker for 30 amp must use at least 10 gauge copper wire size to avoid an unexpected accident. 

2. How many amps can 12 gauge wire handle?

Like we have stated before, the amperage capacity of a wire not only relies on the gauge size. It is also influenced by the materials of the wire and the temperature at which it is operating.

Generally, a 12 gauge non-metallic copper wire can handle 20 amps for standard electrical cables.

On the other hand, if you have a metal conductor like aluminum, 12 gauge wire may carry an optimum of 15 amps. Even, that is the same as in temperature, 12 gauge wire has different ampere depending on the temperatures.

3. How many amps can 16 gauge wire handle?

As we know, the larger the gauge number means the smaller diameter. And the small in diameter show a decrement in electric current. For instance, the 14 gauge wire is 1.63 mm in diameter and supports a 15 amps circuit.

In the case of 16 gauge wire, it is 1.32 mm in diameter. So, based on the thumb rule, it can hold a maximum of 13 amps, which is relatively less than 14 gauge wire. This 16 AWG is usually used for light-duty extension cords.

4. What size wire for 50 amps at 150 feet?

If you want to run with 50 amps at 150 feet, it is best to go for 4 gauge wire. However, the higher the diameter of a wire is identified by the smaller number on the wire.

5. What size wire do I need for 40 amps?

There are different kinds of gauge wires designed to use for various conditions. One of the most common sizes is 8 gauge wire, perfect to use with 40 amps circuit breaker.

6. Can 8-gauge wire handle 50 amps?

8 AWG may transport an utmost of 70 amps in free air. However, it would be best to use a 6-gauge wire if you want something to handle 50 amps.

7. Can 10 gauge wire handle 50 amps?

A few curious minds want to know is it acceptable to use a 10-gauge wire on 50 amps circuit breaker. Here the truth is 50 amp is a large amount of current for a 10-gauge wire. And it might end up overheating or device damage.

8. Can 10 gauge wire handle 40 amps?

When it comes to amperage capacity for 10-gauge wire, it can perfectly carry 30 amps. On the other side, for a maximum of 40 amps, you must need 8 gauge wire.

9. Can 12 gauge wire handle 30 amps?

12 gauge wire is rated for an optimal of 20 amps. But, you will need at least 10 gauge wire to support 30 amps. Even we can say that a 30 amp breaker can not run safely with a 12 gauge wire.

10. What size wire for 30 amps 200 feet?

With a maximum 3% voltage drop and 120V, 3 gauge wire is suitable for 30 amps 200 ft. And 240V with 3% voltage drop, a 6 gauge wire can handle 30 amps.

11. What wire size for 20 amp breaker?

For a 20 amp breaker, it is better to go for a 12 gauge wire. If you use 14 AWG instead of 12 AWG for 20 amp breaker, it can cause severe damage. 

12. What size wire do I need for 50 amps?

For an optimum of 50 amps, you must need a 6 gauge wire size. A breaker with 50 amp is often used to operate many electrical kitchen appliances. For example, many electronic dryers can require 50 amps.

Final Words

The importance of getting the perfect gauge wire for any breaker is essential. It is evident that without a suitable gauge wire, the probability of a disaster happening is high.

That is why we have created the most versatile chart for gauge wire of 30 amp. With the help of this chart, you would be able to select the wire size easily. We kept all the factors in mind while calculating it.

Moreover, the data used by us is gathered from the chart NEC 310-16. Without a doubt, the information we provided is the most reliable one.

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