Electrical Wire Gauges and Types, Sorted by Job
Southwire Romex SIMpull NM-B 12/2 is the standard for interior branch circuits, Cerrowire 14/2 NM-B covers lighting runs for less, and TEMCo 10 AWG THHN is the pick when the run goes through conduit. Low voltage projects are better served by silicone insulated stranded wire.
Southwire Romex SIMpull NM-B 12/2 is the wire most household circuits call for, Cerrowire 14/2 NM-B is the cheaper choice for lighting circuits, and TEMCo 10 AWG THHN is what you want inside conduit. For car audio and electronics, flexible silicone stranded wire is a different product entirely.
Wire is tricky because the right choice is decided by code and application rather than preference, and the labels are dense with abbreviations. Gauge sets current capacity, insulation type sets where it may legally be installed, and strand count sets how easily it bends. We compared published ratings and constructions, and this is general information rather than a substitute for a licensed electrician.
Our top picks
Southwire Romex SIMpull NM-B 12/2 Cable
The yellow jacketed cable that most 20 amp household circuits are built from, carrying two insulated conductors plus a bare ground. The SIMpull jacket has a slicker surface that pulls through joists and holes with noticeably less drag. It is for dry interior locations only.
Pros
- Low friction jacket pulls easily
- Correct choice for 20 amp circuits
- Widely stocked and code familiar
Cons
- Not permitted in wet or buried locations
- Solid conductors are stiff in tight boxes
Cerrowire 14/2 NM-B Indoor Cable
The 15 amp equivalent, used for lighting circuits and general receptacles where the breaker is sized to match. Being one gauge smaller it is lighter, cheaper and easier to route through drilled studs. Never mix it onto a 20 amp breaker, which is the classic dangerous shortcut.
Pros
- Cheaper and lighter than 12 AWG
- Easier to bend into boxes
- Fine for lighting and low draw circuits
Cons
- Only suitable for 15 amp breakers
- Jacket is slightly stickier to pull than SIMpull
TEMCo 10 AWG THHN Stranded Building Wire
Single conductor THHN is what goes inside conduit, pulled as separate hot, neutral and ground rather than as a jacketed cable. The stranded version bends far more easily than solid on longer runs. TEMCo sells in useful spool lengths and a range of insulation colors.
Pros
- Rated for wet locations as THWN-2
- Stranded conductor pulls around bends
- Available in code colors
Cons
- Must be installed in conduit or raceway
- Requires separate spools for each conductor
GS Power 14 Gauge Primary Wire
Copper clad aluminum primary wire aimed at 12 volt automotive circuits, lighting and accessory wiring. The thin flexible insulation routes easily behind trim and through grommets. Note it is not a substitute for pure copper where current draw is high.
Pros
- Very flexible for tight routing
- Sold in paired color spools
- Cost effective for accessory wiring
Cons
- Copper clad aluminum carries less current than pure copper
- Not for household mains circuits
BNTECHGO 16 Gauge Silicone Stranded Wire
Fine stranded copper in a silicone jacket, which stays soft in the cold and tolerates far more heat than PVC. That combination is why it dominates robotics, battery packs and hobby applications. Solder joints and crimps hold well because the strand count is so high.
Pros
- Extremely flexible even when cold
- Very wide temperature tolerance
- High strand count takes solder well
Cons
- Not approved for building wiring
- Silicone jacket nicks more easily than PVC
Striveday 18 AWG Silicone Hookup Wire Kit
A multi color spool set that solves the everyday bench problem of running out of the one color you need. Silicone insulation strips cleanly and resists iron burns during soldering. Aimed at breadboard, model and low current wiring rather than anything structural.
Pros
- Color coding simplifies complex builds
- Resists soldering iron contact
- Strips cleanly without nicking strands
Cons
- Limited current capacity at 18 AWG
- Spool lengths are short in some kits
InstallGear 12 Gauge Primary Wire
A long spool of flexible primary wire for speaker runs, accessory circuits and general 12 volt work where cost per foot matters. Insulation is thin and pliable, which helps when routing through a vehicle. Treat it as low voltage wire and nothing more.
Pros
- Long spool at a low cost per foot
- Flexible enough for tight vehicle routing
- Common colors readily available
Cons
- Lower conductivity than pure copper
- Thin insulation needs grommets at panel passes
What to look for
Gauge is set by the breaker, not by preference In household wiring the conductor size and the overcurrent device are matched, which is why 14 AWG belongs on 15 amp circuits and 12 AWG on 20 amp circuits. Going larger is generally acceptable and sometimes useful on long runs where voltage drop matters, but going smaller is a fire risk regardless of what the load appears to be. Always size the wire to the breaker protecting it.
Insulation type decides where it may be installed NM-B, the familiar jacketed Romex style cable, is approved for dry interior locations only. THHN and THWN-2 single conductors go inside conduit, with the wet rating mattering for underground or exposed runs. UF cable is the one rated for direct burial. Using the wrong type is not a performance issue, it is a code violation with real consequences at inspection.
Solid versus stranded is a workability choice Solid conductors hold their shape, seat firmly under screw terminals and are standard in residential branch circuits. Stranded conductors flex repeatedly without fatiguing, which is why vehicles, appliances and anything that moves use them. Stranded also pulls more easily through long conduit runs, at the cost of needing ferrules or careful technique at terminals.
Low voltage wire is a separate category Automotive primary wire and silicone hookup wire are excellent at what they do and have no place in a wall. They lack the jacket ratings, the code listings and often the pure copper conductor that building wiring requires. Keep the two worlds separate, and if a household circuit is involved, have a licensed electrician confirm the work.
Compared at a glance
| # | Model | Type | Best for | Score | Price |
|---|---|---|---|---|---|
| 1 | Southwire Romex SIMpull NM-B 12/2 Cable | NM-B non metallic sheathed | Best overall | 9.4 | Check price |
| 2 | Cerrowire 14/2 NM-B Indoor Cable | NM-B non metallic sheathed | Best value | 9.2 | Check price |
| 3 | TEMCo 10 AWG THHN Stranded Building Wire | THHN/THWN-2 stranded | Best for conduit | 9.0 | Check price |
| 4 | GS Power 14 Gauge Primary Wire | Automotive primary wire | Best for automotive | 8.8 | Check price |
| 5 | BNTECHGO 16 Gauge Silicone Stranded Wire | Silicone insulated stranded | Best flexibility | 8.6 | Check price |
| 6 | Striveday 18 AWG Silicone Hookup Wire Kit | Silicone insulated stranded | Best for electronics projects | 8.3 | Check price |
| 7 | InstallGear 12 Gauge Primary Wire | Automotive primary wire | Best budget spool | 8.0 | Check price |
Questions worth asking
What gauge wire do I need for a 20 amp circuit?
12 AWG copper is the standard for a 20 amp branch circuit. 14 AWG is only appropriate on 15 amp circuits, and putting it on a 20 amp breaker is a serious hazard.
What is the difference between NM-B and THHN?
NM-B is a jacketed cable containing several conductors, approved for dry interior use without conduit. THHN is a single insulated conductor intended to be pulled inside conduit or a raceway.
Can I use indoor wire outside?
No. NM-B is rated for dry interior locations only. Outdoor and buried runs require UF cable or THWN-2 conductors inside suitable conduit.
Is copper clad aluminum wire acceptable?
It is common and generally fine in low voltage automotive and audio work, where the reduced conductivity can be handled by choosing a larger gauge. It is not the right choice for household mains wiring.
Why is stranded wire used in cars?
Vehicles vibrate constantly, and solid conductors work harden and eventually crack under repeated flexing. Fine stranded wire tolerates that movement, which is why it is standard for automotive and appliance use.
How do I choose wire for a long run?
Voltage drop grows with distance, so long runs often justify going one gauge larger than the minimum. A voltage drop calculation based on length, current and gauge is the correct way to decide.
What do the numbers in 12/2 mean?
The first number is the conductor gauge and the second is the count of insulated current carrying conductors. A 12/2 cable has two 12 AWG insulated conductors plus a bare ground wire.
Do I need a permit to run new electrical wire?
In most jurisdictions new circuits require a permit and inspection, and rules vary widely. Check with your local building department, and use a licensed electrician for anything involving a panel.
The bottom line
For interior branch circuits Southwire Romex SIMpull NM-B 12/2 is the wire to reach for, since the low friction jacket makes long pulls much less punishing. Drop to Cerrowire 14/2 for 15 amp lighting runs, use TEMCo THHN inside conduit, and keep silicone hookup wire for the bench.
