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How Many Amps Can An 18-Gauge Wire Handle?

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Last updated on November 1st, 2022 at 06:54 am

To a non-professional in the electrical field, the figures and measurements of wires and outlets on labels in the hardware store can be very confusing.

Nevertheless, it is essential to know how many amps a wire can accommodate and transport.

The wires are conductors of electricity and serve as paths that direct current to whatever outlet or electrical fixtures you want to install.

Failure to consider the capacity of cables can lead to adverse results like overheating the wires, which could subsequently cause fires.

An 18-gauge wire can handle about 16 amps of current. It is one of the smaller wires in diameter and is commonly used for low-voltage lighting.

How Many Amps Can An 18-Gauge Wire Handle At 12 Volts?

amps 18 gauge wire handle

The number of amps an 18-gauge wire can handle at 12 volts depends on the length of the wire. The longer the wire, the lower the amperage of current.

You can now discern that the correct wire depends on the distance from the power source to the electrical device or outlet than the power draw itself.

 For example, at 7.3ft, an 18-gauge wire can handle five amps at 12 volts. Also, at 12 volts, it can take 15 amps when 2.4ft long. For this reason, it is pretty safe to use 18-gauge wire at low currents.

Can You Run 120 Volts Through An 18-Gauge Wire?

How Many Amps Can An 18 Gauge Wire Handle

Yes, you can run 120 volts through an 18-gauge wire. It, however, depends on what wire is being used to connect.  For this reason, you cannot use an 18 gauge wire to connect a doorbell at 120volts.

Safety will be measured at about 48 volts and below.  It is also dependent on where you want to run the wire. It is neither suitable for any permanent wiring nor connections inside walls.

When choosing cables for your home’s electrical needs, you must ensure that they are suitable for those particular needs; the wire conductors must match the amperage rate of the circuit when installing, rewiring, or extending the circuit.

To ensure that the wires do not overheat and cause fires when there’s a higher voltage running through them, larger wires need to be installed.

Also, the correct wire gauge must be a good fit for the circuit breaker. It is important to note that the amperage of a conductor is determined by the type and number of electrical appliances connected to the circuit.

Therefore, it would help to conform to your geographical location’s local electrical regulations or ordinances.

These will make for a safe electrical connection and guarded flow of power that will guarantee a good and well-maintained circuit system in your home.

Another critical thing to note in selecting gauge wires is the fuse. The wire gauge must reflect the size of the fuse.

The fuse is a protective device, just like a circuit breaker, that prevents the overloading of an electrical circuit.

When too much current flows through the conductors, such as to cause overheating or make the wires melt, a fuse breaks the circuit, thus protecting the wiring and the electrical equipment.

The fuse is essentially made up of a metal that quickly melts. Therefore, if the current flow is overloading through the fuse, the wire heats up, melts, and then breaks the circuit.

Measuring Electric Wires or Cables.

Cables and wires are generally the same; the only difference is that the former is a group of electrical conductors encapsulated in a protective covering known as insulators which I will discuss further.

On the other hand, the latter is simply an electrical conductor. As mentioned earlier, it is essential to know the sizes of wires to know which would be appropriately sized for your circuits.

Wire gauge refers to the physical length of the wire, and it is rated with a numerical designation that is inversely proportional to the diameter of the conductors. But, the larger the diameter of the conductor, the smaller the wire gauge number. 

There are two basic measurements for wires:  AWG ( American Wire Gauge), developed by Northern America, and the British SWG (Standard Wire Gauge).

Unlike the latter, the AWG is the most commonly used measurement system globally.

Below are typical examples of sizes according to the AWG system.

  • 18-gauge Wires
  • 16-gauge Wires
  • 14-gauge Wires
  • 12-gauge Wires
  • 10-gauge Wires
  • 8-gauge Wires
  • 6-gauge Wires
  • 4-gauge Wires

What Is 18-Gauge Wire Rated For? 

It is generally believed that since an 18-gauge wire is thinner, it cannot support a high number of volts. This belief is not entirely accurate.

The gauge of a wire does not limit the voltage transmitted through it. An 18-gauge wire can be rated from 12 volts to 1000 volts depending on the wire’s insulation.

The primary use of the gauge of the wire is to limit the amount of current it conducts from the power source, while the insulation limits the voltage by its thickness.

Insulation is when the transfer of heat or electricity from one conductor to another is prevented by separating such conductors from non-conductive materials.

The non-conductive materials inside the insulated wire or cable make them resistant to electric current.

In addition, the non-conductive materials encapsulate the wire and cable, thereby protecting them.

Insulation protects the wires from the environment and protects the environment from the wires too.

For example, it protects the cables from foreign elements like water which can corrode them and increase their resistance to current, which causes heat to build up, the type of heat that is unsuitable for the system, consequently leading to fires.

On the other hand, the environment is protected by insulation when it prevents current from flowing out of the wire to places it is not supposed to go, for example, where someone touches a ‘naked wire’, causing injury.

Rubber and plastic are the commonly used insulators found on cables today, and they are usually called polyvinyl chloride (PVC) insulators.

How Is Thick 18-Gauge Wire In Inches?

According to the  AWG measurement system, 18-gauge wire is about 0.0403″ thick inches. That is about 1.024mm thick. Therefore, it is one of the thinner wires used for in-house wiring and is relatively safe as it uses low voltage.


When handling wiring projects in the home, you must consider the type of wire that should go with the circuit at the appropriate amps and with the correct voltage.

The 18-gauge wire is one of the standard measurements of wire used in electrical wiring. At 12 volts, the amount of amps this type of wire can handle depends on the length of wire to be used.

You can run 120 volts through an 18 gauge wire, but it also depends on what accessory is being powered and the proper insulation of the cables. Thus 18-gauge wire is relatively safe for wiring in the home.

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