Wire size calculator

Wire Size Calculator
Select Voltage
120V 208V 240V 277V 480V
Select Wire Type
Copper Aluminum
Select Phase
Single Phase Three Phase
Input Amperage Input One Way Distance (in feet)
Minimum Size Required

Electrical wire Code chart

Table for Control electrical wire
Assign electrical cable color from following table

Conductor # First Tracer Color Second Tracer Color
1 Black
2 Red
3 Blue
4 Orange
5 Yellow
6 Brown
7 Red Black
8 Blue Black
9 Orange Black
10 Yellow Black
11 Brown Black
12 Black Red
13 Blue Red
14 Orange Red
15 Yellow Red
16 Brown Red
17 Black Blue
18 Red Blue
19 Orange Blue
20 Yellow Blue
21 Brown Blue
22 Black Orange
23 Red Orange
24 Blue Orange
25 Yellow Orange
26 Brown Orange
27 Black Yellow
28 Red Yellow
29 Blue Yellow
30 Orange Yellow
31 Brown Yellow
32 Black Brown
33 Red Brown
34 Blue Brown
35 Orange Brown
36 Yellow Brown

480 V AC

Phase A = Brown
Phase B =Orange
Phase C = Yellow
Ground = Green

120 V AC

Hot = Black
Neutral = White
Control = Red
Ground = Green

24 V DC

Positive = Blue
Negative = Yellow
Control = Orange
Ground = Green

Electrical wire size table

Here are only few cable types and their applications example:

600 V THHN Copper conductor: For use in general wiring application and power in conduit.
600 V RHW-2 Copper Conductor: For use in harsh environments for general wiring direct burial.
300 V UL type PLTC: This is a multi-pair instrumentation cable: For use in instrumentation and process control applications

Copper Electrical Wire
Copper is the common used because copper is a very good conductor, and is easy to mold and bend.

Aluminum Electrical Wire
Aluminum is cheaper and more abundant than copper. It is also easy to shape and bend.
More important for electrical designer is to select the right size of electrical wire . The following link is the method of how to determine cable size.

Delivering electricity safely throughout your home

Types of electrical wire

Wire and cable make up the delivery system for electricity in your home. Running from the main breaker panel or fuse box to outlets, appliances and fixtures indoors and out, wire and cable must be sized and installed appropriately to keep electricity running through your home—and to pass an electrical inspection.

While the terms wire and cable are often used interchangeably, technically wire is one electrical conductor and cable is a group of conductors, or wires, encased in sheathing. The National Electrical Code (NEC) and local building codes regulate the types of wire and cable that can be used in specific electrical applications, as well as the manner of installation. Check with your local building inspector before you start any wiring and cable electrical project and be sure to obtain required permits. When your work is complete, always have it inspected for compliance with local codes to ensure that it has been safely installed.

This buying guide will explain the different types of wire and cable and their uses, so you can feel confident you’re making the best and safest selection for the electrical system in your home. 

Factors to Consider

  • Wire – Label information, color, applications
  • Cable – Applications, NM, UF cable, armored cable, metal-clad cable, coaxial cable, cat5e cable



Label information, which is printed on wire coverings, provides all of the information you need to choose the right wire for your home. That information includes:

  • THHN or THWN – These letters represent the most common types of individual wires used in residential applications. The letters represent the following NEC requirements: •  is for the thermoplastic insulation on the wire;
    •  H is for heat resistance;
    •  H is for high heat resistance up to 194° Fahrenheit;
    •  W means the wire is rated for wet locations, such as outdoors; and
    •  N means the wire is impervious to damage from oil or gas.
  • Material — Most wire will be marked “CU,” for copper, the most common conductor of residential electricity. Because electricity travels on the outside of copper wire, wires are insulated to protect against fire and shock. Older wire could be aluminum or copper-clad aluminum.
  • Maximum voltage rating — This will be a number such as 600, which indicates the maximum voltage the wire can carry.
  • Gauge – This number indicates wire size. The most common gauges are 10, 12 or 14. Larger numbers represent smaller sizes or gauges of wire. See the table below for more about wire and cable gauge.


  • Colored insulated wires other than white or green are always hot. Black, blue and red wires are typical hot wires in residential wiring.
  • White insulated wires are always neutral.
  • Green insulated and bare copper wires are always ground wires.


  • Run wires in conduit for unfinished areas such as basements or attics and outdoors for devices like landscape lighting. To learn more about conduit, see our Conduit Buying Guide


NM-B cable is the most common form of indoor residential electrical wiring. The “NM” stands for non-metallic, which refers to the flexible, generally PVC sheathing surrounding the cable. The “B” represents a heat rating of 194° Fahrenheit. This rating ensures wires can operate at certain levels without overheating, melting the insulation and creating fire and safety hazards. Inside the sheathing are at least two thermoplastic insulated wires of the same gauge, though different cables can have different gauges. As with wire, all the information you need to know about NM-B cable is printed on the sheathing.

  • Type — This label will most commonly read NM-B. 
  • Gauge — This number is the gauge of the individual wires inside the cable, such as 14, 12, 10, etc.
  • Number of wires — This number follows gauge. For example, 14/2 indicates that there are two 14-gauge wires (a ground wire, if part of the cable, is not included in this number) within the cable.
  • Grounding — The word “GROUND” or the letter “G” indicates the presence of a ground wire.
  • Voltage rating — The most common rating for residential use is 600 volts, though the number can vary. The number indicates the maximum voltage the wire can safely carry.
  • UL — Indicates that the cable is safety certified and approved for use by Underwriters Laboratories.

Wire is sized by the American Wire Gauge (AWG) system. The larger the number the smaller the wire. The following table provides information about amps (the amount of current a wire can safely carry), and wattage (the rate of electrical energy used by an appliance), and common uses of different gauges of wire and cable.

NM-B applications: Run NM-B cable behind walls and ceilings, inside floor cavities and in other unexposed areas. It is not designed for running along the outside of a wall, such as in an unfinished basement. Use NM-B indoors only, in spaces that are dry and free from moisture. Exposure to water can subject the wires to corrosion. Since the insulation is rated to handle only a certain level of heat, you’ll want to avoid placing wires near heat sources such as hot water pipes or heating ducts. Also, do not bury NM-B in cement, concrete, plaster or underground.

UF cable is similar to NM cable, but is rated for in-ground and damp-area installation. In fact, UF stands for underground feeder. From the outside UF cable looks like NM-B cable, but the wires are embedded as a group in solid thermoplastic (rather than individually encased in flexible thermoplastic). Like NM cable, UF cable comes in a variety of gauges to meet all electrical code requirements and is labeled with the same information carried on NM cable plus the designation UF.

Armored cable (AC) is wire enclosed in metal sheathing. Often called by the trade name, BX, AC consists of insulated hot and neutral wires, plus a bare bonding wire, all wrapped in paper. The metal sheathing acts as the grounding conductor. AC is relatively expensive and difficult to work with, so it’s not often used in new residential construction. It can be found in older homes, however. AC is rated for indoor use only.

Metal-clad cable is similar to AC, except that the wires are wrapped in plastic rather than paper. In addition, MC cable has a green grounding wire, because its metal sheathing can’t be used as a ground. MC cable is rated for indoor use only, though, like AC, it’s not often used in residential applications. Both MC cable and AC require:

  • Special cutting tools, which cut the sheathing but not the wires;
  • Bushings, which are inserted in the ends to prevent the sharp edges of the metal from damaging the wires; and
  • Special electrical boxes and connectors.

Coaxial cable, usually called coax, is a metallic cable most often used to carry television signals and connect video equipment. Coax features a central wire conductor covered with a dielectric or non-conducting insulator surrounded by mesh or a metal sheath and covered by a thin plastic layer for protection. For more information on coax, see ourNetworking Cables Buying Guide.

Category 5e cables, also called cat-5e, are the industry standard for unshielded twisted-pair cables (UTP) for connecting phones, computer networks, home automation networks and audio/video distribution systems. Often generically called Ethernet cable, the copper cabling typically consists of 4 pairs of wire (8 total conductors) wrapped in a single jacket. For more information on cat5-e cable, see our Networking Cables Buying Guide.

American Wire Gauge (AWG) system

Conduit fittings are used to connect runs of conduit together or to connect conduit to electrical devices. The types of fittings you use will depend on whether you’re using metallic or non-metallic conduit, and the types of connections you need to make. In addition, electrical fittings are sized to fit the different diameters of conduit. To learn more about the different types and uses of conduit, see our Conduit Buying Guide.

Local building and electrical codes regulate the type of conduit and fittings that can be used in specific applications. Check with your local building inspector before beginning a project and be sure to obtain any required permits. When your work is complete, always have it inspected for compliance with local codes and to ensure that it has been safely installed.

This buying guide will explain the different conduit fittings, so you can feel confident you’re purchasing the right fittings for your project.

Electrical Fittings — Adapters, bushings, couplings, elbows, straps, and connectors

AdaptersAdapters connect different types of material or different thread sizes together. For example, an adapter might connect a run of nonmetallic conduit to a metal junction box with solvent cement on one end and threads on the other.

BushingsBushings are inserted into the ends of metal conduit to keep the sharp edges from damaging the wires that run through the conduit.

CouplingsCouplings connect runs of the same type of conduit to create a longer straight line.

· Metallic couplings are generally attached to metallic conduit with set screws or with compression. However threaded couplings can be screwed directly onto the end of threaded conduit.

· Nonmetallic couplings are attached to nonmetallic conduit with solvent cement.

ElbowsElbows join runs of the same type of conduit together to turn corners or to change direction in a gentle sweeping curve, rather than a sharp right angle, which makes it easy to pull wires through without damaging them.

StrapsStraps hold conduit to the wall or joist to keep the conduit from sagging or breaking.

ConnectorsConnectors are used to join runs of conduit together or to join conduit to outlet boxes, load centers or other devices.

I bought new light fixtures for my bathroom, but when I removed one of the old fixtures I found there was no junction box. There is no stud near where I need to place the junction box I would like to install. Please help.

You should be able to install the light fixtures using an old-work electrical box (also known as a remodel box). It’s sold at hardware stores, home centers and electrical supply stores, and is available in any number of rectangular and round configurations. Your choice depends on whether you’re installing a switch, an outlet receptacle, a group of switches or a ceiling light. We show a rectangular box that can be used to install a switch, a receptacle or a fixture in a wall. (For more information, see the National Electrical Code.)

Unlike a new-work box that is attached to wall studs (and is installed when the house is built), an old-work box is installed after the house is built. It attaches directly to the drywall, provided the drywall is in good enough condition so that it can support the box and electrical equipment attached to it.

To install the box shown above, hold it so its face is against the wall and trace the outline of the box body with a pencil. (Don’t trace around the box flanges.) Then cut around the line with a drywall saw. After removing the waste piece of drywall, pull the electrical wires into the box and set the box into the hole. Then tighten its two screws. Doing this pulls the box’s clamps against the back of the drywall, fastening the box tightly in place between its flanges and the clamps. Next, make the light’s electrical connections, install the light fixture’s mounting strap to the box and mount the fixture to the strap.

The box shown is typically used for installing switches, and outlet receptacles, but it can support a wall fixture up to 6 pounds, according to the manufacturer. The box has a small opening but its extended depth gives it a large volume (20 cu. in.). This allows plenty of room for cable and electrical connections, and makes it especially handy for electrical installations in a tight spot.

When installing this or any other junction box, follow the manufacturer’s instructions and make sure that the electrical power to the circuit is turned off. The work that you do must conform to current electrical codes.

Before starting, check with your local building department. Some municipalities allow homeowners to make minor electrical modifications, but others require that an electrician do the work.

For more information on old-work junction boxes, visit Carlon’s Web site at http://www.carlon.com.

Read more: Homeowners Clinic Expert Q & A – May 2005 – Popular Mechanics

Electrical boxes enclose wire connections for applications such as a light switch, electrical outlet or light fixture. Specific boxes are designed for use indoors, outdoors, for attaching to the outside of walls, for behind walls and other applications.

In addition to enclosing wiring connections, electrical boxes:

  • Provide convenient access to electrical components for regular maintenance and upgrades and
  • Offer protection that grounds electrically charged wires and prevents short circuits that could lead to fire.

The National Electrical Code and local building codes regulate the types of electrical boxes that can be used in specific applications, as well as the manner of installation. In addition, code requires that electrical boxes not be covered with drywall, paneling or other wall covering, but with electrical box covers that can be matched to all boxes.

Check with your local building inspector before you start any electrical project and be sure to obtain required permits. When your work is complete, always have it inspected for compliance with local codes to ensure that it has been safely installed.

This buying guide describes the different types of electrical boxes, their materials and applications so you can feel confident you’re choosing the right box for your project.

Factors to Consider

Types of Electrical Boxes 

Handy boxHandy box – A handy box mounts on the surface of a wall and can contain light switches or receptacles. Handy boxes are ideal for areas where behind-the-wall installation is not possible or is difficult.

Junction boxJunction box – In a junction box, wires connect only to each other, never to a switch, receptacle or fixture. This type of electrical box allows circuits to be safely split and branched into different directions.

New-work box
New-work box – Electrical boxes installed as part of a new construction project are called new-work boxes. New-work boxes are mounted directly to studs or joists, or placed between two studs using a bar hanger before drywall is applied.

Old-work box
Old-work box – Remodeling boxes, also called old-work boxes, are electrical boxes designed to be installed after drywall has been hung. For example, if you need an additional outlet for a home office or theater. Old-work boxes hang on the drywall with clamps built in to the box. Our How to Install a Remodeling Box Project Guide walks you step-by-step through the installation of a remodeling box.

Outdoor boxOutdoor box – Available in metal and nonmetallic units, outdoor boxes protect wiring from the elements with gaskets, sealed seams, and in some cases watertight covers.

Shapes and Sizes 
Electrical boxes come in a variety of shapes and sizes, each designed for a specific purpose.

Standard rectangular boxStandard rectangular box – These most common boxes house a single electrical switch or outlet.

Square boxSquare box – Also called double-gang box, these boxes house two devices, either a combination outlet/switch or a pair of outlets or switches in one location.

Round or octagonal boxRound or octagonal box – Houses lightweight fixtures or safety devices in the ceiling such as a light or smoke and carbon monoxide alarms.

Ceiling boxCeiling box – Used for heavier fixtures, such as ceiling fans or chandeliers. Be sure to choose one that is specifically designated to support the extra weight.

Electrical boxes are constructed of either metallic material, such as aluminum, steel or cast iron, or nonmetallic material, such as PVC or plastic. Each material provides the necessary protection to keep your home’s electrical system working safely under specified conditions.

Metal boxesMetal boxes have characteristics that differentiate them from plastic or PVC. Many local building codes require metal junction boxes because they are durable and ensure long lasting performance. In addition, metal boxes should be used for exposed indoor applications, such as with conduit in an unfinished basement.

Plastic or PVC boxesPlastic or PVC boxes are an inexpensive and easy-to-install solution for both new-work and old-work situations where they can be placed behind drywall. Plastic boxes should only be used with nonmetallic cable.


Box coversBox covers: Once a box has been installed and devices have been attached to the wiring inside, code requires an appropriate cover.

  • Interior light switch and outlet covers can be plain or feature decorative designs to complement your décor.
  • Exterior covers need to be watertight, and for outlets, you’ll want an in-use cover, which allows the outlet to stay covered completely even when something is plugged into it.
  • Junction boxes have plain covers that hide the inside wires, yet still allow convenient access.
Braces and bar hangersBraces and bar hangers are mounted between joists to allow lights or other devices to be positioned in a variety of locations. For example, when installing a ceiling fan in a finished ceiling, inserting a brace through a hole cut in the ceiling between joists allows for easy positioning and minimal ceiling repair work. Some bar hangers come with an electrical box attached.

Extension ringsExtension rings allow you to increase the depth of your electrical box, providing more space to accommodate a larger number of wires.

Adjustable depth boxesAdjustable depth boxes can be adjusted to allow installation of the box flush with the surface of a wall, no matter the depth of the wall material.

Installation Tips and Hints

  • For new construction installations, diagram the room and be sure you have enough electrical boxes to accommodate all the light switches, outlets and fixtures you need.
  • When working in finished areas, use a stud finder to locate studs and make sure they don’t interfere with the placement of a new box.
  • Trace an outline of the box on the wall where it will be installed to mark cutting lines. Utility knives work well for cutting holes in drywall, keyhole saws are good for plaster and saber saws are useful for wood.
  • Light switches are generally installed about 42 in. from the floor.
  • Power outlets are generally 12 in. from the floor.
  • Plan for future changes by clearly labeling all wires.
Electrical Junction Box covers and types of boxes used to handle wire.


A breaker panel, also known as a load center, service panel, breaker box or electrical panel, is a steel box that holds multiple circuit breakers wired to circuits that distribute power throughout your home. Circuit breakers turn the power to your home on and off to protect wiring from damage by “tripping” when an electrical short or overcurrent occurs. You may consider replacing your electrical panel or adding a sub-panel if a need for additional circuit breakers exceeds the capacity of your current breaker panel or if you want to upgrade from fuses to circuit breakers. It’s important to note that a new breaker panel will not provide more power to your home. If your home needs more power overall, use the services of a professional electrician to upgrade the power, a process that will include a new breaker panel as well as other accessories, such as new cables and a new electrical meter. This buying guide will help you understand what to look for when selecting a breaker panel, so you can feel confident you’re choosing the right breaker panel for your needs.

Before purchasing a new breaker panel, take time to assess your present and future electrical needs and plan accordingly. Check with local authorities and your utility company to be sure you select a panel that conforms to code and all local requirements.

Factors to Consider
Components – Main breaker, circuit breakers, bus bars, neutral bus bars, grounding bus bars
Types – Main breaker, main lug, sub-panel, transfer switches
Amps – Varies by need, ranges from 100 to 200
Circuit Breakers – Single pole, double pole, GFCI, AFCI
Electricity comes into your home through wires that connect to your breaker panel. Understanding the components in a panel can help you make an informed decision when making your selection. A typical breaker panel consists of these primary components:

The main breaker is a large double pole circuit breaker that limits the amount of electricity coming in from outside to protect the circuits it feeds. It also identifies your breaker panel’s amperage capacity.

Circuit breakers are stacked in the panel and have an ON/OFF switch that controls the flow of power.

Bus bars receive power from the two thick black wires that bring power in from the electrical meter. The bus bars in turn carry power through the circuit breakers to the circuits.

Neutral bus bars connect to the main circuit’s neutral wire. The neutral bar provides the contact point for the white wires that return electricity back to the breaker panel after flowing through the black wires to power a device. Your home’s main grounding wire also connects to the neutral bar.

Grounding bus bars unite all the grounding wires from the breaker panel’s various circuits and connect them to the ground bar. It is also connected to a grounding conductor that leads underground, the metal enclosure and, if it’s the main service panel, to the neutral bar; the ground bar is not connected to the neutral bar at sub-panels.

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There are different types of breaker panels to choose from, each of which meets a certain code requirement or application, depending on your area. Check with local authorities to determine which type of panel meets your local compliance requirements.

Main breaker panels have a built-in main breaker which can be used to shut off all power to your residence. A main breaker is a large double-pole circuit breaker that limits the amount of electricity coming in from outside to protect the circuits it feeds. It also identifies your breaker panel’s amperage capacity. Main breakers can be installed when the meter and feeder cable are within 10 ft. of the panel.

Main lug panels do not have a main breaker. Instead the line wires run to lugs. This type of breaker panel requires a separate disconnect. The main breaker, which would function as the disconnect, may be located at the meter, or if the main lug panel is used as a sub-panel, it may be connected to the breaker at the main panel. In the event of a fire, the separate disconnect at a meter can be helpful to fire authorities, who don’t have to enter the building to cut power.

Sub-panels are separate breaker panels that can contain new circuits, allowing you to readjust energy distribution to better handle your typical usage patterns. Also known as service or circuit breaker sub-panels, they can be a good solution when a breaker panel doesn’t have enough slots to add new circuits. A sub-panel is also ideal for situations where multiple circuits are needed in a single separate area, like a workshop or greenhouse. Be aware, however, that sub-panels do not increase the amount of available power. If an increase in electricity is needed, contact your local utility company or an electrician for increased service.

A sub-panel is typically powered by a circuit from within the main panel and does not have its own main disconnect.

The amp rating of the circuit in the main breaker panel must be the same or smaller than the rating of the sub-panel connected to it. Put another way, if the sub-panel is rated at 30 amps, the maximum amperage of the circuit in the main breaker would be 30 amps.

The only limit for the number of sub-panels you can have is the number of available circuits in the main breaker panel.

Transfer Switches are a type of sub-panel that transfers portable generator power into electrical power through your breaker panel. If you live in an area where storms are common, you may have a permanent back-up power generator that uses an alternative power source, like propane or natural gas. The generator can be wired directly to the household breaker panel, providing a seamless switch from utility service to back-up power when the electricity goes out. Some generators come with a transfer switch that carries the same rating as the home’s main breaker panel. There are two models of transfer switches:

Automatic transfer switches require a larger initial investment but provide continuous protection for homeowners.

Manual transfer switches are less expensive and require you to power up the generator and manually switch the load to the back-up system.

Read our Transfer Switches Buying Guide to learn more about transfer switches.

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Breaker panels are identified by the amount of amperage they provide. For example, a breaker panel of 100 amps will only allow 100 amps of electricity to flow through it without tripping. They’re also identified by the number of circuits they accommodate. For example, a 150-amp, 30-circuit panel can handle 150 amps of electricity with room for 30 circuit breakers.

When replacing your panel you’ll want to match the amperage capacity of your current model, or if your power needs have grown, upgrade to the capacity you need. The amperage will be identified on your current panel’s main breaker.

Amps typically range from 60 amps in older homes to as much as 200 in new construction.

One hundred amps is the minimum required by the National Electrical Code (NEC), but 150 is increasingly common.

While 100-150 amps are generally suitable for most homes, breaker panels are also available in 200- and 400-amp units.

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Circuit Breakers
The last factor to consider is to know the number and type of circuit breakers you require. This can vary, based on your needs. When making your selection, be aware that a circuit breaker is sized to operate at 80% of its rated capacity. This means that to operate safely, a circuit breaker rated at 20 amps should only carry a load of 16 amps.

You can calculate the total load for the circuit by adding up the loads of the devices that will run on it. These are usually identified on a sticker or label on the devices or appliance. If the load is calculated in watts, use this formula: amps = watts divided by volts. Example: 1,400 watts divided by 120V = 12 amps.

Different types of circuit breakers include:

Single pole, or 1 pole, circuit breakers provide 120 volts in various amp ratings. Single pole circuit breakers rated 15 to 20 amps are typically used for receptacles and lighting.

Double pole, or 2 pole, circuit breakers provide 240 volts in various amp ratings. Double pole circuit breakers are typically used for appliances and hot water heaters.

Arc fault circuit interrupters (AFCI) are designed to shut down power to a circuit when they detect arcs of electricity caused by worn or damaged wires. AFCIs are used to protect circuits in bedrooms and common areas.

Ground fault circuit interrupters (GFCI) break a circuit instantly when a short is detected. They are used to protect circuits in wet areas, like bathrooms, garages, unfinished basements and kitchens.
If you are upgrading your breaker panel to accommodate more 240V circuits for appliances that draw high current, like air conditioners and stoves, read our Circuit Breakers Buying Guide to learn more about these and other circuit breakers.

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