I am trying to add a new outlet by branching off an existing one (for my mounted tv).

The cable that goes into the box contains one white cable and one black cable that has an extra red wire (as part of this box is on a switch).

I am comparing the new 14 gauge wiring with the existing wiring I have in the box and it seems smaller (somewhat). The housing on the wiring is white which is why I was under the impression that it was 14 gauge.

In this picture below the wire, i am holding is the new wire I just purchased. Where the solo white wire is the existing electrical outlet wire.

enter image description here

Am I just being paranoid / is it just the wire housing that makes it seem bigger?

  • 4
    You should be looking at the circuit breaker to choose the wire size, If a 20 amp breaker it would need 12 gauge if 15 amp breaker 14 would be the correct size but 12 can be used. Almost all nm or romex used to be white so going by the sheath color is not a good way to I'd the size.
    – Ed Beal
    Commented Jan 26, 2018 at 20:44
  • It would help to edit your question using the terms wire, cable etc. in the manner mmathis discusses. Otherwise it's very easy to get confused. Commented Jan 27, 2018 at 2:06

3 Answers 3


Yep. White was standard for #14 through #8 or even #6 until a few years back, when color codes came into fashion. Read the stamp or printing on the sheath to be sure.

  • 2
    And by "fashion" we mean not all companies do it even today. You can buy white #12 if you call around. Commented Jan 27, 2018 at 2:17

What you're seeing is the insulation on the old wire, which is white (and red and black on the other wires in the cable), but the sheathing on the new cable. It's just a confusion of terminology.

A wire is a single strand of copper (or aluminum), often coated with a colored insulation (except in the case of ground wires, which are allowed to be bare). The size of the wire is denoted by its gauge (in the US, at least): #14, for example. The color of the insulation is sometimes an indication of its purpose, although that's not always the case. Black is usually hot, white is usually neutral, red is switched-hot or traveller - but again, these are standards, not rules.

Several wires bundled together form a cable, which is coated with a colored sheath. The color of the sheath typically denotes the size of the wires contained within, although that's not always the case (especially near outlets, as the yellow sheath of 12/2 or 12/3 cable often gets sprayed by paint or texture by the drywall crew, making it look white). Cable is named or marked by the size and number of the conductors (excluding ground): 12/2 has 2 #12 wires plus a ground; 14/3 has 3 #14 wires plus a ground.

The best way to know what size the wire is is to measure its cross-sectional area or diameter, or check the sheath of the cable for any markings which indicate the size of the wires within.

  • 3
    If you have a typical wire stripper with slots for different gauge wire this can act as a wire gauge. Put the #14 and #12 slots against each wire and you'll figure out what size they are.
    – Stanwood
    Commented Jan 27, 2018 at 3:55

I made this mistake recently, assumed my home was wired with 14 gg based on the sheath color, also assumed breakers were 15 amp (it's just what I'd seen in my previous home)... Went to work with it, and saw the same thing, read the sheath and it is 12gg, breakers, yup, 20 amperes. Now I have an extra 25' of 14 gauge, and had to buy more 12 gg.

  • 1
    Was this intended as an answer? We're not a discussion forum.
    – isherwood
    Commented Jan 7, 2021 at 21:57

Not the answer you're looking for? Browse other questions tagged or ask your own question.