Skip to Content

How to Connect 12-3 Wire to 12-2 Wire [4-Step Solution]

Connecting electric wires isn’t as easy as you may think. It becomes even harder if the wires aren’t exactly the same. That’s why you have to proceed carefully with enough knowledge to avoid any risks. 

How to connect 12-3 wire to 12-2 wire? 

Start by disconnecting the area and checking for voltage. After that, grab a wire cutter and start cutting both wires. When you’re done, use a wire stripper to strip the wires. Twist the black with black and white with white wires by a plier. Put wire caps on twists and the red wire afterward. 

Anyways, that was just a short summary of the entire discussion. There are still some basic fundamentals that you need to know. 

Let’s dive into more details!

What’s the Difference Between 12-3 & 12-2 Wires? 

In case you haven’t done wiring before, we’ll go through the basics. Don’t worry it’s not a science class and I will be super brief. 

Both wires have conductors and a ground wire.  It functions as a neutral wire but isn’t exactly the same. 

Many homeowners often don’t know neutral wires and what they are

As you can see the naming has two numbers separated by a hyphen. One of them means the wire’s thickness. The other means the number of active conductors.

The 12 in the “12-2” wire stands for gauge. Gauge is a wired measurement for thickness. Simply put, a 12 gauge wire is thicker than a 6 gauge wire. 

All that’s left is the 2 at the end of the naming. It means the wire has 2 active conductors. They have a plastic wrapping of black and white.

The inside of the 12-3 wire is exactly the same except for one difference. There’s an extra conductor. The third conductor is wrapped in red.

The red wire can be used in many different things. A lot of households have ceiling fans using red wires

Connecting a 12-3 Wire With a 12-2 Wire: 4 Simple Steps

This process is done in several steps and there are some precautions to take. But first, you’ll need some necessary tools. 

To save you some time, I’ve listed them for you- 

  • Voltmeter or Multimeter
  • Wire Stripper
  • Wire Cutter
  • Utility Knife 
  • Plier
  • Twist-On Wire Cap

Grab these tools as soon as you can to get started! 

Step 1: Take Necessary Precautions & Prepare Yourself

Wiring jobs aren’t meant to be taken carelessly. If you aren’t careful enough, you can hurt yourself really bad. 

The wires are also a direct source of electricity, so mistakes aren’t an option. Remember that a simple mistake can cause death. That’s why you must take several precautions for your own safety. 

The first thing that you’re going to do is to turn the electricity off. It can be done by turning off the switches of the circuit breaker. 

But that’s not enough assurance. Because of that, you’ll need a voltmeter or a multimeter to test the voltage. 

If you’re still seeing some voltage, turn off the main circuit breaker. 

If you don’t have access to a multimeter, don’t worry. I’ve already picked some of my favorites for you-

Product 1
Product 2

You can now choose whichever you like more and get started!

Other than this, make sure the area is dry and no water is nearby. Wet areas are extremely risky for obvious reasons. 

Besides, try to have someone stay by your side while you work. Being safe always pays off. 

Step 2: Cut The Wires 

To do this step you’ll need a wire cutter first. Grab that tool and get ready. 

Let’s take the 12-3 wire first. It has 3 different colored wires inside; white, black, and red. Start by cutting the head of all 3 wires. 

For cutting, you can also use a utility knife. But wire cutters work more efficiently. Remove the protective wrapping from them. 

Leave the red wire alone for now. When you’re done, take the 12-2 wire and do the same. 

Step 3: Strip & Twist the Wires

Many people often can’t tell which is positive between the white and black wire. The black wire is always positive and the white wire is always negative. 

And that’s exactly how we’re going to connect them. We’ll connect the wires by matching the colors. 

Take a wire stripper and strip some insulation from all the wires. Usually, a half-inch of insulation is fine. Take the plier and twist the stripped ends with each other. 

Keep twisting until they’re tight and won’t get separated. 

Step 4: Cap The Joints & Red Wire

It’s time to use those twist-on wire caps that I have told you to get. Simply grab them and place them securely over the twist. 

For the red wire, repeat the same process. With a wire cap on top of it, it’s much safer.

And you’re done! Make sure nothing is left open and has been capped off. Like wires, you can also connect or change an outlet to GFCI using this method. 


Question: What is the red wire for in a 12-3?

Answer: 12-3 wires have white, black, red, and ground wires. Among them, the black and red are hot wires. But the red is slightly different. They’re called traveler wires. 

Question: How many amps will 12-3 wire carry?

Answer: A 12 gauge wire with 3 conductors can carry about 20 amps of current. That’s the maximum limit allowed by the US government. But the ratings can differ. 

Question: What is the green wire for in 12-3?

Answer: The green wire usually means a ground wire. They can also be bare copper wires too. Some ground wires can be in green but have yellow stripes on them. 

Final Words

That was everything on how to connect 12-3 wire to 12-2 wire. I hope these were helpful enough to paint you a clearer picture. 

One parting tip from me as a reward of reaching till the end. If you see other colors except for black or white, call an electrician instead. 

Finally, good luck and happy splicing!