Wire Gauge Chart
Lower gauge number means thicker wire and more current.
Compiled by DIY Repair Guide · reviewed 2026-09-05 ·how we research these
American Wire Gauge (AWG) runs backwards from intuition: the smaller the number, the thicker the conductor. A 14 AWG wire is thinner than a 12, which is thinner than a 10. Every three steps down roughly doubles the cross-sectional area.
The wire size determines the maximum breaker you may fit, and never the other way around, and that relationship is what the whole chart is really about.
The Chart
These are the standard sizes for copper conductor in residential branch circuits at 60°C termination, which is what household devices are rated for.
| Wire size (AWG) | Max breaker | Typical use |
|---|---|---|
| 18 AWG | — | Low-voltage: thermostat, doorbell |
| 16 AWG | — | Light-duty extension cords |
| 14 AWG | 15 A | Lighting, bedroom and living-room receptacles |
| 12 AWG | 20 A | Kitchen, bathroom, laundry, garage, outdoors |
| 10 AWG | 30 A | Electric dryer, water heater, window AC |
| 8 AWG | 40 A | Electric range, small subpanel |
| 6 AWG | 55 A | Large range, EV charger, subpanel |
| 4 AWG | 70 A | Subpanel, large service feeder |
| 2 AWG | 95 A | Service entrance, large subpanel |
The Rule That Matters
A breaker protects the wire. It does not protect the appliance. It is sized so that it trips before the conductor can overheat inside a wall.
This is why fitting a 20-amp breaker to a circuit wired in 14 AWG is dangerous rather than merely non-compliant. The 14 AWG cable is rated for 15 amps. The 20-amp breaker will happily pass 19 amps indefinitely, and the wire heats up in a cavity you cannot see, next to insulation and timber.
The corollary is useful: you can always fit a smaller breaker than the wire allows. Running 12 AWG on a 15-amp circuit is fine and gives you headroom to upgrade later.
Never increase a breaker size to stop nuisance tripping without confirming the wire supports it. Check the gauge printed along the cable sheath. If it says 14, the circuit is a 15-amp circuit regardless of what breaker someone fitted.
Distance Changes the Answer
The chart above assumes short runs. Over distance, resistance in the conductor causes voltage drop. The appliance receives less than 120 V, motors run hot and inefficiently, and lights dim.
The usual design target is to keep voltage drop under 3 percent on a branch circuit. Past roughly 50 feet on a 15- or 20-amp circuit, and much sooner on higher-current runs, going up one gauge is the standard remedy.
- Detached garages and sheds are where this bites most often. A 100-foot run to an outbuilding routinely needs a size up from the chart.
- 240 V circuits tolerate distance better than 120 V for the same power, because the current is halved.
- Voltage drop is not a code violation in most cases. The NEC treats 3% as a recommendation rather than a requirement. It is still poor practice to ignore.
| Circuit | Wire | Upsize beyond roughly |
|---|---|---|
| 15 A | 14 AWG | 50 ft |
| 20 A | 12 AWG | 60 ft |
| 30 A | 10 AWG | 75 ft |
| 40 A | 8 AWG | 90 ft |
| 50 A | 6 AWG | 110 ft |
Copper and Aluminum Are Not the Same
Aluminum conducts less well than copper, so it needs to be roughly two gauge sizes larger to carry the same current. Where copper 12 AWG handles 20 amps, aluminum needs 10 AWG.
Aluminum is still normal and correct for large feeders and service entrances, where the cost saving is large. What causes trouble is aluminum branch wiring, used widely in US homes built between roughly 1965 and 1973. It expands and contracts more than copper, which loosens terminations over time, and loose terminations arc. It has a documented association with house fires.
If you have aluminum branch circuits, do not simply fit standard devices. Connections require CO/ALR-rated devices or approved copper pigtail connectors, and this is properly electrician work.
Reading What You Already Have
The gauge is printed along the outer sheath of the cable, along with the conductor count and whether a ground is included. A marking reading 12/2 WITH GROUND means 12 AWG, two current-carrying conductors plus a bare ground.
Modern non-metallic cable is also color-coded by size, which is a quick check but not a substitute for reading the print. Older cable predates the convention.
| Sheath color | Gauge | Circuit |
|---|---|---|
| White | 14 AWG | 15 A |
| Yellow | 12 AWG | 20 A |
| Orange | 10 AWG | 30 A |
| Black | 8 or 6 AWG | 40–55 A |
| Grey | — | Underground feeder cable (UF), any gauge |
Extension Cords Follow the Same Physics
An extension cord is a wire run, and the same distance and gauge relationship applies, which is why a long thin cord running a space heater gets warm.
| Load | Up to 25 ft | Up to 50 ft | Up to 100 ft |
|---|---|---|---|
| Light duty, under 7 A | 16 AWG | 16 AWG | 14 AWG |
| Medium, 7–10 A | 16 AWG | 14 AWG | 12 AWG |
| Heavy, 10–15 A | 14 AWG | 12 AWG | 10 AWG |
A warm extension cord is undersized for what it is carrying. Space heaters in particular should be plugged directly into a wall outlet. They draw close to a full 15-amp circuit continuously, which is exactly the condition cords are worst at.
Common questions
What size wire do I need for a 20 amp circuit?
12 AWG copper as a minimum. 14 AWG is rated for 15 amps only, and pairing it with a 20-amp breaker means the cable can overheat before the breaker ever trips.
Can I use 12 gauge wire on a 15 amp circuit?
Yes. Oversizing the conductor is always permitted. The breaker protects the wire, so a heavier wire is simply better protected. It also leaves the option of upgrading to a 20-amp circuit later.
Does wire gauge get bigger or smaller as the number goes up?
Smaller. AWG runs inversely: 14 AWG is thinner than 12, which is thinner than 10, and roughly every three gauge steps down doubles the cross-sectional area.
What gauge wire for a 100 foot run?
Usually one size larger than the chart suggests, because of voltage drop. A 20-amp circuit that would normally use 12 AWG typically wants 10 AWG at 100 feet to stay within a 3 percent drop.
Is aluminum wiring safe?
Aluminum is fine and standard for large feeders. Aluminum branch wiring in homes from roughly 1965 to 1973 is the concern. It loosens at terminations and has a documented fire association. It needs CO/ALR-rated devices or approved copper pigtails, fitted by an electrician.