Knowing which 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, 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!
A Rule of Thumb: What are the correct wire sizes for 70, 80, 100, 125, 150, 200, 400 & 600 Amp Service & Breakers?
What electrical components do I need for various project? The rule of thumb that techs will usually go by is that for a 70 amp circuit breaker, 4-gauge copper wire is the right one to go with. For a 80 amp you need a 4-gauge copper wire. For a 100 amp service, you will need a 1-gauge wire.
For 125 and you will need a 1-gauge copper wire. For 150 amp you will need a 1/0-gauge copper wire. For 200 amp service you will need a 250 kcmil-gauge copper wire. For 400 amp service you will need a 600 kcmil-gauge copper wire. For 600 amp you will need a 1500 kcmil-gauge wire.
It’s important to realize that these rules of thumb come with certain limitations, such as the material and the ambient temperature.
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.
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 take a look at 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 right wire is a gauge 3. For 80 amp service, the right wire is gauge 2. The right wire 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 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, and if you’re more cautious, a 4. That is, of course, assuming the right conditions such as temperature.
Let’s say you have 8-gauge and a 10-rated lying around at home, and you want to know if you can use these with the circuit breaker. The 8-gauge, nor the 10-gauge can be coupled with this breaker. Simply take a look at the chart further down the page.
For 70 amp, the right wire 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 circuit breaker with this rating, you can use 4-gauge copper at an ambient temperature of 140°F.
If you’re working with 80 amp service, you need a gauge 4 copper wire, whereas it would need to be a 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 gauge 1. However, that is only if you don’t consider the material. We’ll go into a little bit more detail below.
For a sub panel, you need to either get a gauge 1 made of aluminum, whereas a 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.
Be sure to consider the table below to see the various products we recommend when it comes to sub panels, entrance cable & more. When you click through to the product, you may have to make the right selection for some of the products so as to follow the electrical recommendations provided above.
To be on the safe side, the right wire for 125 amp service is a gauge 1 copper or a 2/0 aluminum. Press this link to scroll to the chart below, or look at 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 you can go with when looking at copper.
Suppose you have a circuit breaker at home with this rating, 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.
For 200 amp service, the right wire size is a 250 made of aluminum or a 3/0 made of copper, according to the chart. Here’s a table with the different sub panel, breakers, 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 copper 600 kcmil can handle that amount of power – take a look at the NEC electrical cable chart below.
The right 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|
What is a gauge?
The gauge is the diameter of the product, 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; 6, 4, 3, 2, 1, 1/0 , 2/0, 3/0, and 750.
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 tool 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 consider 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 AWG 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 different electrical components always need to be compatible with one another.
If you have a 60 amp circuit breaker for your water heater, clothes dryer, or air conditioner that you have no idea which product 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 anything less than the recommended 14-gauge could lead to performance issues, at best. For electric furnaces, you need at least a 4, because of the amount of current they consume.
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 diameter is way smaller for your circuit breaker, the current flowing 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 measurement instrument for the purpose is a quick and easy way to answer your questions about your product’s diameter. We use the AWG system 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, is the highest current it can handle given the various conditions, like the material it was made from and the ambient temperature.
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. 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, while the smallest is the 40. The former lets more energy flow through it at any given time than the smaller ones will.
Frequently Asked Questions
Let us take a good look at other queries and questions that commonly pop up while dealing with electrical work and appliances.
What’s the difference between stranded and solid wire?
Both solid and stranded versions see a lot of use in electrical equipment but how are they different? A solid type consists of a single solid core wire but the stranded type is made up of an assembly of smaller thinner wires.
Stranded wires are more flexible since they consist of many smaller sub-parts. It is also significantly more malleable and offers the advantage of not splitting or getting damaged when being used in devices, control panels, and other uses. This is why it is frequently used in small and cramped spaces where sub-parts must be connected and fit together regardless of the awkward positions they end up in.
The solid type is thicker and ideal for spaces where high durability and heavy current are required. This can include porch areas, backyards, and even workshops set up in the garage where you need to power heavy equipment like drill presses and chainsaws. The thick size and high resistance to weather conditions mean it can be used widely in the electric parts of vehicles and big buildings.
Wire versus Cable
Both of the above terms may seem interchangeable to a lot of folks, but few know the significance of each. The basic wire is one single conductor whereas a cable is many different conductors grouped. While the cables are protected by an outer layer of the sheath, the wire usually goes bare or has a coating of PVC on top for protection and prevention of accidents.
The unit of a wire is the gauge or thickness, which we have referred to above. But in the case of the cable, the measuring unit is the total number of wires a cable consists of and their thickness.
On one hand, wires are used to carry small electrical loads and transmit telecommunication signals and other small parts like bulbs and vehicle parts. On the other hand, the cables are used to transport huge loads of electrical currents.
The types of cable include coaxial cable, twisted pair cable, multi-conductor cable, and fiber-optic cable. As the name suggests, a multi-conductor table means the joining together of many different cables and its goal is to reduce noise, hum, and cross-talk. Coaxial cables consist of two conductors, one on the inside and one on the outside running parallel to it. These are generally used in televisions. You’ll generally find the twisted pair type wherever data and telecommunication transportation is required. Since the twisting of the two conductors reduces noise, it is perfect for the task of transmitting data signals through long distances.
Is it ‘Gauge’ or ‘AWG’?
American Wire Gauge or AWG, is the standard used in most of North America and refers to the thickness. It is used to denote the current carrying capacity of the wire and the cross-sectional area. The use of this standard all over North America ideally means that you can purchase a 14 AWG wire from two different vendors in the region and you will find they are the same thickness. The ‘gauge’ can be used as a shortened way of expressing AWG, but this must always be confirmed by the seller. Sometimes manufacturers use the term ‘gauge’ to market cables that almost certainly are not in AWG units.
What is a breaker box/sub-panel? What is the difference between a Main Panel and Sub-panel?
The main panel is also known as the service entrance panel. Here the power company’s current first enters the home and is further distributed to the rest of the household. It’s also the first safety net that protects your home from any kind of electrical damage or fires. If you suspect any faults in the circuit, you can directly switch off the main panel and take your home out of the power grid of the electricity supplier.
The sub-panel on the other hand is like a miniature main panel that doesn’t have a direct connection from the power utility company, but rather feeds off the main panel’s current. Its purpose is quite similar to the main panels in that it protects appliances from shorting or faulting. They also contain circuit breakers and fuses to detect any surcharge of electricity and immediately stop the current to avoid fires. But then how are sub-panels different?
Sub-panels are different as they take their power from the main panel and their main purpose is to help you organize your home’s electrical circuit in a manageable manner. You could also use a sub-panel to avoid overcrowding in the main panel. Overloading is a serious fire hazard and you can avoid this by distributing your home into the area with each having its sub-panel.
Subpanels can also be used to isolate certain areas which have different power usage. For instance, a garage workshop will put a great load on the main panel with its heavy machinery. You can avoid this by setting up a separate sub-panel for the garage. And best of all, in the event of any short or fault, you can simply isolate the area with the problem and turn off the respective area’s sub-panel while the rest of the house can remain powered as usual.
What is the difference between Neutral and Earth lines?
The simplest way to explain the Neutral and earth lines is to take a look at a basic three-pin socket. Each pin corresponds to Earth, neutral, and phase. While the phase line carries the current, it’s the neutral line that makes for the return for the balancing of the flow, and the earth line is the safety net during the entire process.
Earth line: The fluctuation that comes with alternating current in household or workplace use can be dangerous if not directed elsewhere. That is why the earth line makes sure to take the extra current directly into the ground so that no shorts or accidents take place. A rod is usually used to direct the extra current away under faulty conditions. During normal conditions, this line usually stays current-free.
Neutral line: This line is a return path for the alternating current, connecting the flow back to its origin point. Even though it carries no current, without this line the circuit is incomplete. It is also known as the zero potential point since here the return path provides a way to make the total of the current zero. In this way, both neutral and earth lines are safety lines and precautionary measures are taken to reduce chances of a short in the scenario of a faulty discharge of current.
What is the difference between MCB and FUSE? Which is better?
Both of these devices are used as safety nets to completely stop the flow of the circuit whenever there is an overload. However, there are some differences between the two.
The most obvious difference between the two is that a fuse is a self-destructing metal piece that melts whenever there is an overload to protect the rest of the circuit. But a Miniature circuit breaker has a switch that trips when there is an overflow of current or a fault.
This essentially means that a fuse will have to be replaced every time there is an overload while an MCB can be used again and again. Another disadvantage of the fuse is that it doesn’t give any indication of an overload and must be checked every time.
The working principles of the fuse and MCB are also very different. While a fuse works by detecting thermal and electrical properties, an MCB works on electromagnetic principles.
A fuse is significantly cheaper than an MCB and is ideal for homeowners who require a cheap, low-breaking capacity option.
What is a base meter? When is it time for a replacement?
A base meter is a protective enclosure around the electric meter to keep the machinery and wires dry and in proper working condition. It is also responsible for receiving the supply of current from the power utility company and sending it to the main power panel of the house. Although it is the power utility company that provides the meter box, the homeowner is responsible for all other attachments. Keeping the meter box and meter base in the appropriate condition is hence very important for the house to be powered.
If you spot any of the following signs, your meter base may be in trouble: flickering lights, appliances, and devices not working, and partial outages in the house. If spot any visible damage to your meter box and base, it also may be time for a replacement. This can include corrosion on the inside or outside due to the weather conditions or torn and broken wires or lugs. Apart from all these conditions, the updating of meters to standard building and electricity codes is a major reason to get your meter base replaced. It is common for meter boxes to get upgraded to a 200A capacity as older homes generally have 60A capacity meters installed. If you have a large home or property, a 400A capacity meter would be more appropriate.
What is the National Electrical Code?
The NEC is used as a benchmark for safe electrical installation, design, and inspection in all 50 states of the United States of America. It is part of the publishing by the National Fire Protection Association. Although it is not established by federal law, it is commonly followed by all of the states.
Basic NEC rules and Codes
Size of circuit breaker: For non-motor loads, the maximum loading for a breaker is cut off at 80%. Under no circumstances can the breaker be larger than the ampacity, unless it is for motor loads.
General design guidelines: lights and outlets should be set up on different circuits. This will allow maximum loading on light circuits and leave capacity for other outlets as well.
Outlets circuits must have GFI protection if located in residential locations. Any places with portable equipment and machinery, for example, any garage areas, workshops, shops, warehouses must also have GFI outlets. Apart from this, each piece of fixed machinery, for instance, drill presses, welding machines, etc. must also have its own GFI-protected circuit.
Service size: The minimum service for a very small building is 100 A and 20 circuits. It is advisable to do load calculations for larger places.
Underground – Use XLP-USE for underground wiring, with AWG copper minimum.
Protection of cables and conduits: Conductors must be inside a cord, trench, raceway, or cable tray.
Outdoor receptacle: Each home must have one front and one rear receptacle which is easily accessible. For this purpose, it is advised it should be located no more than 6 and a half feet above the ground.
Receptacles used to supply power to the pumps and motors of spas, Jacuzzis and pools must be at least 10ft away from the pool if without GFCI. If the receptacle is GFCI protected, it can be located no closer than 6ft.
Light fixtures located outdoors do not require GFCI protection.
Light fixtures of low voltage should not be any nearer than 5ft to indoor water structures like spas, pools, hot tubs, and Jacuzzis.
Internet, telephone, and other types of wiring should be located at least 10ft away from the top of the water surface of indoor water structures.
Underground wiring must be covered with conduit.
Buried underground or exposed wiring must always be listed for its use. UF cable type is best known for underground purposes as it can be dug and settled underground without the use of a conduit.
Wiring carrying equal to or less than 30 volts must be located 6 inches deep underground.
Now that you have sufficient knowledge of Amp wire size, NEC codes, and basic electrical knowledge like gauges, meter bases, sub-panels, and circuit breakers, you can make the right electrical choices for your home. Remember to always get a professional licensed electrician to get work done in your home or office.