Romex is the everyday name for the cable that wires most homes. Technically, Romex is a brand name for NM-B cable, which stands for nonmetallic sheathed cable, but the name has become so common that many people use it for the cable itself. If you have looked inside a wall or an electrical box in a modern home, you have almost certainly seen it.

Here is what Romex wiring is, how it is built, and where it can and cannot be used.

What Romex is made of

Romex, or NM-B cable, bundles the conductors a circuit needs inside a single flexible sheath. A typical cable contains:

• One or more insulated hot conductors
• An insulated neutral conductor
• A bare copper grounding conductor
• A plastic outer sheath that holds everything together

The plastic sheath is what makes it nonmetallic, and it is why the cable is easy to run through the wood framing of a house. The conductors are copper, which is the standard for residential wiring.

How to read Romex cable

Romex is labeled and color-coded so you can tell what it is. The printing on the sheath lists the wire gauge and the number of conductors, written like “14-2” or “12-3.” The first number is the wire size, and the second is the number of insulated conductors, not counting the ground. A “14-2 with ground” cable has 14-gauge wire, two insulated conductors, plus a ground.

The sheath color also indicates the wire size on modern cable: white for 14 gauge, yellow for 12 gauge, and orange for 10 gauge. This makes it easier to identify circuits at a glance.

Where Romex can be used

Romex is designed for dry, protected, indoor locations. It is at home:

• Inside walls, ceilings, and floors
• In dry interior spaces
• Where it is protected from physical damage

This covers the vast majority of residential branch circuits, which is why it is so widely used.

Where Romex should not be used

Just as important is knowing where Romex does not belong. It is generally not suitable for:

• Wet or damp locations, such as outdoors or in contact with the ground.
• Exposed areas prone to physical damage, where it needs the protection of conduit.
• Some commercial and specific applications where other wiring methods are required.

For those situations, electricians use other methods like conduit with individual conductors, UF cable for underground runs, or metal-clad cable. Using the right wiring method for the location is a basic code and safety requirement.

Why it matters for your home

Understanding Romex helps you recognize modern, properly installed wiring versus older or improper work. If you see cable run in a wet or exposed area where it should not be, or older wiring that predates NM-B entirely, those can be signs that an electrician should take a look. When Romex is installed correctly in the right locations, it is safe, reliable, and exactly what most homes are built with.

Romex is the common brand name for NM-B cable, the nonmetallic sheathed cable used to wire most homes. It combines copper hot, neutral, and ground conductors in a plastic sheath, is labeled by gauge and conductor count, and is color-coded by wire size. It belongs in dry, protected indoor spaces and should not be used in wet or exposed locations, where other wiring methods are required.

Stella Electric handles wiring, rewiring, and repairs using the correct methods for every location, serving homeowners across the Baltimore area and throughout Maryland with flat-rate pricing and no overtime charges. If you have wiring questions or concerns, we can help. Financing is available on qualifying projects.