Home Improvement Skills & Specialties Electrical Wiring & Circuits

Wire Nuts Sizes and How to Choose: A Guide

Whether you're rewiring a receptacle, installing a new light fixture, or updating your sprinkler system, chances are, you'll need to connect multiple wires together securely to make your new device or outlet work.

The easiest way to make these circuit wire connections is with a little piece of plastic or ceramic called a wire connector, or wire nut— and knowing the right wire nut sizes to use for each type of project is key in making your DIY wiring last and preventing loose connections.

wire nuts

The Spruce / Michele Lee

Wire Nut Sizes by Color

Standard wire nuts come in five main sizes, which are usually color-coded to show the ranges of wire gauges— or wire thicknesses, measured in AWG— that they can be used for. Bigger wire nuts can also be used for wires that carry higher voltages, or more power.

The colors can vary, but as a general rule:

  • Gray wire nuts can accommodate wires between 22-16 AWG, up to 300 volts.
  • Blue wire nuts can accommodate wires between 22-14 AWG, up to 300 volts.
  • Orange wire nuts can also accommodate wires between 22-14 AWG, but of higher voltages up to 600 volts.
  • Yellow wire nuts can accommodate wires between 18-12 AWG, and up to 600 volts.
  • Red wire nuts can accommodate wires between 18-6 AWG, and up to 600 volts.

You may also come across green wire nuts, which are used to join copper grounding wires, or purple wire nuts, which can be used to join aluminum and copper wires.

Tip

Remember, wire gauge is measured and labeled so the lower the number is, the thicker the wire is. This means gray wire nuts are for the smallest wires, and red ones are for the largest.

Types of Wire Nuts

There are a few main types of wire nuts and connectors you can use for different electrical wiring projects in and around your home.

Standard

Standard, or twist-on wire nuts, are color-coded by the wire sizes they can fit. Twist-on wire nuts can be round, square, or have built-in wings to make twisting easier to do by hand. They're usually made from a durable plastic that acts as insulation for the wires, and can withstand the heat generated by regular household electrical connections.

Deep Skirt

Deep skirt wire nuts are similar to standard ones, but they have a longer skirt, or body, to cover longer lengths of exposed wire and provide more insulation and protection to the connection.

Weatherproof

Underground and waterproof wire connectors are designed with a silicone sealant filling to protect the wires from any moisture present in outdoor wiring situations. Underground wire nuts in particular will be rated for direct burial.

High-Temperature

Made of ceramic or thermaplastic to prevent melting, high-temperature wire nuts are used in heaters and lighting fixtures. Just keep in mind that ceramic is much more fragile than plastic, so connections will need to be made with care and pre-twisting your wires is best to avoid any excessive force.

Push-In

Push-in wire connectors are flatter than the standard variation, and involve pushing the wires through allocated transparent slots instead of twisting them together. They accommodate a smaller range of wire gauges than standard nuts— typically 22 to 12 AWG.

Special Connections

There are also wire nuts that look similar to the standard varieties, but are designed for special connections, such as creating one point for grounding when rewiring an outlet, or joining aluminum and copper wires together in older homes. These are usually green and purple, respectively.

Wire Nut Sizes by Fixture

Standard wire nuts can be used for a majority of wiring projects in the home, ranging from outlet receptacles and control panels to fans, garage doors, and doorbells. However, there are some fixtures around the house that will require a special type of connector.

For example, it's best to use high-temperature or ceramic wire nuts when working on connections within light fixtures and heaters, and you'll need waterproof or underground wire nuts for outdoor lights, sprinklers, and pool pumps.

If you're ever unsure what your project calls for, it's always safest to call a professional to help.

How to Use Wire Nuts

Always follow manufacturer instructions, as they can vary by product. But here's the standard procedure:

  1. Strip about 1/2 to 3/4 inch of insulation from the end of each wire with a wire stripper.
  2. Hold the wires together so the ends are aligned.
  3. As an optional step, twist the wires clockwise with pliers before applying a wire nut for a more secure connection.
  4. Select the appropriate size of wire nut, place it over the wire ends and push into the wires while twisting the nut clockwise.
  5. Tighten the nut as much as possible, until there is no bare wire showing. You can also give the nut a final short twist with a pair of linesman pliers.
  6. Give each wire a little tug to make sure it is securely held by the nut. If anything is loose, remove and start over.
Wire insulation stripped 1/2 to 3/4 inch on ends with wire strippers

The Spruce / Kevin Norris

Stripped wires held side by side so ends are aligned

The Spruce / Kevin Norris

Wire ends pushed into yellow nuts and twisted around

The Spruce / Kevin Norris

Wires tugged to check its secure in nut

The Spruce / Kevin Norris

Tip

If you're connecting a solid-copper wire to a stranded-copper wire, strip the stranded wire about 1/8 inch further back, and line up the wires to where the insulation ends before following the rest of the steps above.