Knowing which wire size to pick is important, so you can use the right one for your equipment that requires electricity. In case this is your first time reading about the topic, we are covering some of the basic things to know about it.
In a hurry? Buying recommendations
If you’re wanting to buy a circuit breaker, a sub panel, service wire, a transfer switch, a meter socket or a fuse for either your 70, 80, 100, 125, 150, 200, 400 or 600 amp service, we’ve found all the products we recommend. We’re sure our work will save you both time and money!
For those that already know what a gauge is, and the importance of finding the right product depending on what it is going to be used for, we’ll just right into it and share a wire ampacity rating chart where you can figure out yourself what it is that you need. Simply scroll down a little bit. Also, this article was made due to the increasing popularity of our original article. Whether you’re doing gasless MIG welding, welding aluminum or anything else, choosing the right one is crucial.
If you’re looking for a chart that can show you the right wire size for 70, 80, 100, 125, 150, 200, 300, 400 or 600 amp of service, simply scroll down the page a little bit further.
Table of content
A Rule of Thumb
While we encourage you to check out the chart below to find the right products for your project, there are general rules of thumb that techs go by, which we have included in the chart as well.
For a 70 amp, the safest wire size is a gauge 3. For 80 amp service, the safest wire size is gauge 2. The right wire size for 100 amp service is gauge 1. 125 amp requires a wire size 2/0. For 150 amp, the right wire size is 3/0. For 200 amp service, you will need a wire size 250 kcmil. For 300 amp, the right wire size is 500 kcmil. 400 amp service requires a wire size of 1,000 kcmil. For 600 amp service, we recommend a wire size of 1,750 kcmil.
We’ve got the size chart you need, that easily lets you see the electrical cable requirements for both aluminum or copper.
Below is a table based on conductor temperatures of 140°F unless otherwise stated, taken from the NEC 310.16.
|Ground wire, service entrance, circuit, breaker size chart rating|
|Service or Feeder Rating (amp)||Aluminum conductor||Copper conductor|
|70||#2 AWG||#4 AWG|
|80||#1 AWG||#3 AWG|
|100||#1/0 AWG||#1 AWG|
|125||#3/0 AWG||#1/0 AWG|
|150||#4/0 AWG||#3/0 AWG|
|200||350 kcmil||250 kcmil|
|300||700 kcmil||500 kcmil|
|400||1,250 kcmil||750 kcmil|
|600||2,000 kcmil (194°F)||1,500 kcmil (167°F)|
If you are unsure of which type of material you are dealing with, or you don’t know the right temperature, we always suggest erring on the side of caution, why the column to the right shows you the lowest number in the different columns. It’s always better to choose a bigger diameter if you are unsure about any of the conditions that could influence the performance.
As you can see for 60 amp, you will really want a 6 gauge wire size, and if you’re more cautious, a 4 gauge. That is, of course, assuming the right conditions such as temperature.
Let’s say you have an 8-gauge and a 10-gauge lying around at home, and you want to know if you can use these with a 60 amps circuit breaker. The 8-gauge, nor the 10-gauge can handle a 60 amp circuit breaker. Simply check out the chart further down the page.
For 70 amp, the right wire size is either a gauge 3 aluminum or a gauge 4 copper, assuming there aren’t other factors impacting the performance.
The requirement depends on whether it is aluminum or copper and the ambient temperature, as you can see from the chart further down. For a 70 amps circuit breaker, you can use 4-gauge copper at an ambient temperature of 140°F.
If you’re working with 80 amp electricity, you need a gauge 4 copper wire, whereas it would need to be a size 2 if you are going for aluminum instead. Be sure you get the right one for your subpanel and breaker!
The rule of thumb for 100 amp service is that you go with a wire size gauge 1. However, that is only if you don’t consider the material. We’ll go into a little bit more detail below.
For this amount of service, you need to either get a gauge 1 wire made of aluminum, whereas a gauge 3 will work if it is made of copper, which applies to a breaker & subpanel as well. These recommendations are based on conductor temperature ratings of 167°F. Press this link to scroll to the chart below. It is important that you scroll further down the site so that you’ll come across the table that shows the right recommendations as the temperature will affect the right choice for your sub panel, entrance cable and other electrical components.
Check out the table right below to see the various products we recommend for 100 amp when it comes to sub panels, entrance cable, service wire & more.
To be on the safe side, you will need to make sure you’re either using gauge 1 copper or a 2/0 aluminum wire size for 125 amp of service. Press this link to scroll to the chart below, or check out the table right below this to see the sub panel and breaker that we recommend.
For 150 amp, as per the chart below, you’re need a 3/0 wire size made of aluminum, whereas a 1/0 is the smallest size you can go with when looking at copper.
Suppose you have a 150 amps circuit breaker at home, and you would like to make use of it.
In this case, you will need 1/0-gauge copper at an ambient temperature of 167°F or 2/0-gauge aluminum at an ambient temperature of 194°F.
200 amp service requires a wire size 250 made of aluminum or a 3/0 size when made of copper according to the chart. Check out the table right below to see the sub panel, breakers, service wire and more that we recommend for this level of service.
For 300 amp service, you will want copper wire of size 500 kcmil to be able to handle the load.
400 amp service requires an aluminum wire size of 1000 kcmil, whereas a 600 kcmil copper size can handle that amount of power – check out the NEC electrical cable chart below.
The appropriate wire size for 600 amp service is at least 1500 kcmil assuming a temperature of 167°F of the conductor.
Full wire size chart for 70, 80, 100, 125, 150, 200, 300, 400, 600 amp & more
|Max amp for||Aluminum||Max amp for||Copper||Our recommendation|
|Wire Gauge Size||167°F||194°F||140°F||167°F||194°F|
What is a gauge?
The gauge is the size of the diameter, basically. This determines how much electrical current it can safely carry. If you have ever been to the electrical section of a hardware store, you will notice it come in several options.
Instead of referring to it using its actual thickness, people would refer to it using its gauge size, 6, 4, 3, 2, 1, 1/0 , 2/0, 3/0, and 750 gauge wire.
It is inversely proportional to the diameter, which means the higher the number, the smaller the diameter. If it is not written on the product itself or is unclear, you can use a thickness gauge to determine it. Getting the right diameter is important because it determines the maximum current it can safely handle. Using an incorrect one could lead to serious problems in the long run. So before deciding which to buy, first check how much electrical current it will handle by identifying the devices you plan to use.
The United States, along with 65 other countries, use the American wire gauge as the unit of measure. Other countries use the Imperial Standard, which was defined by the British Board of Trade.
Choosing the right one
They usually burns if you use the incorrect one. It is advisable to know the correct one to prevent this from happening. The bad thing is that most people are not aware that your choice makes a difference. People often make the connections themselves without consulting or calling a licensed electrician. It could lead to serious issues when done incorrectly.
When the setup involves the circuit breaker, you should take extra precautions. Installing the right components will greatly prevent common issues from happening. In most cases, issues arise because of an incorrect one. The gauge and breaker need to be compatible with each other.
If you have a 60 amp circuit breaker for your water heater, clothes dryer, or air conditioner that you have no idea which gauge you need, read through the next section as we guide you in understanding the basics.
What happens when you choose the wrong one
It is a common misconception for people to think that as long as the ends of the wire fit a connector, there will be no issues. It is not the case for circuit breakers. People who are unaware of their importance often use too small gauges to connect their circuit breakers. Smaller diameter ones are cheaper than the bigger ones, which is why people who are unaware often go for the cheaper one, thinking it is not going to make any difference. Sadly, it is only going to cost them more in the long run.
Using a larger one for your circuit breaker is often the best way to go. The only negative effect this has is on your budget, which will cost you more upfront. When picking a larger one, you end up spending more than what you may need. However, it is not going to cause any damage to your circuit breaker. Instead, it can better handle the electrical current flowing through it.
But if you find yourself having the incorrect one, here are the things that might happen.
|Drop in performance||Melted insulation|
A drop in performance
If you connected appliances to a circuit breaker using one that is too small, achieving peak efficiency may be impossible. The appliances can only receive a part of the energy it requires to operate at peak performance. In effect, your appliances will be unlikely to achieve their optimal performance.
For example, you have a 15 amp circuit breaker, which you need to use for light fixtures at home. Using a service wire that is less than the recommended 14-gauge could lead to performance issues. For electric furnaces, you need at least a 4-gauge.
Whether you are doing welding in order to combine metal with those precision joints, or you’re powering a metal lathe, make sure to see what the requirement are for that piece of equipment, as you might simply be using the wrong cord, why you’re not getting the performance you were looking for.
It can start a fire
A burning electrical component that leads to starting a fire is the worst case. Although modern circuit breakers have their safety measures, it may not be enough if the load is too much.
For example, a common safety measure for modern circuit breakers is the trip mechanism. When the circuit breaker experiences an overload, it will trip to cut the current from passing through, preventing any damage from happening. However, having a trip mechanism does not prevent a fire from happening.
A smaller diameter can handle less current, which makes them more resistant to the flow of energy. However, if the gauge is way smaller for your circuit breaker, the current flowing through the wire is more than what it can handle. Due to high resistance, heat generates and will eventually lead to the melting.
Damage to the equipment
Aside from performance drop issues and the possibility of starting a fire, using a smaller one may damage your equipment in the long run. When the supply of power is not stable, it may bust your equipment.
Before proceeding with this section, you should know that it is important to have a licensed electrician handle any electrical work. However, it helps to know some of the basic electrical things, such as the right gauge. The chart electricians use as their reference will differ depending on the region.
Using a standard gauge instrument is a quick and easy way to know the size. We use the American Wire Gauge system, commonly referred to as AWG, in the United States to determine it. The AWG defines the diameter of solid round wires, which is otherwise known as the gauge. The capacity, commonly known as the ampacity, is the highest current it can handle.
When referring to the table below, note that the AWG value is opposite to the diameter. A higher AWG refers to a smaller diameter, which means an 8-gauge can support a higher capacity than a 10-gauge. The chart below defines the diameter in inches and millimeters. The chart should help determine which one to choose.
From the table, the one with the largest diameter is the 0000-gauge, while the smallest is the 40. The former lets more energy flow through it at any given time than the smaller ones will.