I need to replace the cables in one room which has many outlets. Currently the older wiring is labeled 12/2 WG. There is another wire also white (back when) right along side but it doesn't say what gauge it is. Should I replace all with 12/2?

One has to be fished through to the 1/2 bath and is right on the edge of the outside wall. Eek. They all worked fine until a laborer cut through two of them. I am not afraid to do the wiring as long as I am sure that they are both 12/2 gauge.


1 Answer 1


The wire gauge you need can be determined by checking the breaker for that circuit - if it's a 15 A breaker, you can use #14 gauge wire; if it's a 20 A breaker, you need #12. In general, lighting circuits are on 15 A breakers and wired with #14 wire, and receptacles are on 20 A breakers and wired with #12 wire. This convention is relatively modern, though, so your 1975 wiring may not follow it.

There is never a problem using bigger wire than needed, so even if the existing wiring was #14, you can replace it with #12 - just don't replace the breaker! A 20 A breaker needs #12 wire throughout the entire circuit.

You can also get a tool to measure the size of the wire. Something like this:


Or this multi-purpose wiring tool:

Home Depot

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