12 Gauge wire looks like 14 gauge

I know that if it looks like 14 gauge it probably is but here I go…

So I had the awkward experience where a home owner wished to be present at the inspection and wanted to look over my shoulder during the electrical. I noted that the wire looks to be 14 gauge wire and the home owner apparently saw the note and said the it was 12 gauge… His argument was that as a DIY project he used single strand hot 12 gauge wire that “appears thinner” because it is single strand wire. I call BS, but I just thought I would ask my fellow inspectors before I recommend an electrician to evaluate it.

Where in the picture is the wire in question?


Don’t see any solid 20 gauge there. Don’t guess you ever will in a service panel.


There is breaker that is rated 15 amp, just above it the breaker is 20 amp and the wires appear to the same size. I also have no idea where the single strand wire is because everything I have seen so far is the standard multi-strand romex.

Why were you making a note that the wire was a #14? Was it on a 20 amp breaker?

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Yes the #14 wire is on a 20 amp breaker. I just wanted to fact check this home owner in case I was missing something. I have never heard of #12 wire appearing thinner, but that is why I double check.

Now i’m confused. Didn’t take much. When you say single strand we think you mean solid (as opposed to stranded). Doesn’t matter how the wires get there - NMC or individual wires in a conduit - 20 amp breakers will have 12 gauge wire, 15 - 14 gauge. Just ignore the idiot clients that follow you around. When we do converse with them we don’t try to teach them technical stuff; it takes too long and you will both end up feeling stupid.


Homeowner is correct, at least in part! When you are trying to determine size you, ideally, should always go by the bare end of the conductor, not its insulation and or the jacket/sheathing. Here is an example, tell me which wire is 12 and 14 gauge?

All you need right here.

Seller informed our company that portions of the electrical system were installed by the current homeowner. Recommend having a licensed electrician to review the electrical panel. Recommend contacting the local AHJ for any permit requirements.

Insurance will not cover damage that may result from an incident that could be attributed to an amateur install.


A member named Sean Fogerty has developed (3D printer) a set of plastic wire gauges that may help you deal with curveball questions like this.


I agree, the insulation thickness doesn’t tell you much unless you know that type of insulation you’re looking at. The only true way to determine the conductor size (other than reading the size printed on the insulation or cable jacket) is to measure the copper.

Yeap, and too often I find no exposed amount of conductor to check, it’s all inside the terminal… impossible to tell for certain what # it is.

Or Aluminum, as the case may be.

Yes good point.

Was this the Seller (Homeowner) that was looking over your shoulder? If not my client, I just really do not divulge anything while doing the inspection except to my client.

And I really Don’t Want Anyone in close proximity (arms length) of me or the panel when I have it open (anymore). Had to quickly slap a client’s hand away once when he proceeded to say what is? and started sticking his finger where he shouldn’t…happened once, never again.


I would be interested. Is it compact?

The one on the right looks like 12 to me. Am I right?

Wow, that is very interesting indeed. Thank you!