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What Does Romex or NM Mean?

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Romex Brand Electrical Wire

Romex® Brand Electrical Wire

Image © Southwire
Summary: Romex® is a brand of non-metallic (NM) building wire made by Southwire.  NM is used to refer to any type of electrical wiring sheathed in a plastic coating.

Origin of the Name

The name comes from the Rome Cable Corp. of Rome, NY, which originally produced the wire. The "rome" part comes from the company's name. No one is quite sure where the "x" came from, though. Rome Cable was founded in 1936, and filed for bankruptcy in 2003. Now the Romex® brand is owned by Southwire and is an actual trademarked brand. So, there is really no such thing as a lower-case generic "romex" but trademarked Romex® instead. Just like Kleenex or Jell-O.

Compare Prices on Romex® Wire

I've always got some Romex® on hand, even though I infrequently do electrical work.
  • Romex® 12-1 Wire. My advice: don't buy anything less than 100 ft. Those 25 ft. rolls don't take you very far.
  • Romex® 14-3 Wire. This is a thinner gauge wire mainly for lighting applications. Southwire calls it SIMpull®, their brand-name for the slippery coating on the plastic casing to make it easier to pull through.

Romex Brand Is a Matter of Preference

Some electricians may have an individual preference. But walking around any job site, you'll see all brands of NM wiring. Since Romex® may be pricier than other brands of NM wire, the electrician could end up using any brand of wire.

Quality of Romex Brand vs. Other NM Wire

Though opinions differ, I've used all kinds and haven't found that to be the case. Romex® brand costs more than other brands, too.

Although, admittedly, there is a subtle difference. Maybe it's just psychological, but I find the plastic sheathing on brand-name Romex easier to rip and easier to strip. Could it be that the sheathing is slightly softer? Could it be that my brain is softer to think this? Who knows. All I can say is that I've encountered some real uncooperative NM wiring along the way, but Romex tends to be more consistent.

Why Use Romex® or Other NM Over Other Types of Electrical Wiring

It's definitely easier for the lesser experienced homeowner to work with plastic-sheathed wiring. Romex® or NM is:
  • Lighter than metallic sheathed wiring, so easier to handle.
  • Easier to pull through holes in studs because of the smooth sheathing.
  • Easier to cut--just use a set of side-cutting pliers. Smaller gauges can even be snipped with the cutters on a wire stripper.
  • NM cable is usually cheaper.
  • Easier to rip back the cable sheathing--it's just plastic, not metal.

What Does NM Mean?

NM refers to the general class of non-metallic electrical wire. The "non-metallic" refers not to the coating on the wiring inside but to the outer sheathing.

Why Specify That It Is "NM"?

Because metallic sheathed wiring is also available.
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