Wire Gauge by Amps: Quick Reference
The single most important rule in residential wiring is to match the wire gauge to the circuit breaker, never the other way around. A breaker protects the wire, so a wire too small for its breaker can overheat before the breaker ever trips. The chart below covers the common copper NM-B Romex gauges used in homes, based on the 60 degrees Celsius ampacity column that NEC 334.80 requires for NM cable.
Common Household Wire Gauge Chart
| Wire Gauge (Copper NM-B) | Amp Rating | Typical Breaker | Common Uses |
|---|---|---|---|
| 14 AWG | 15 amps | 15 amp | General lighting and receptacle circuits |
| 12 AWG | 20 amps | 20 amp | Kitchen, bath, garage, and laundry receptacles |
| 10 AWG | 30 amps | 30 amp | Electric water heaters, AC condensers, dryers with 10/3 |
| 8 AWG | 40 amps | 40 amp | Electric ranges, larger AC, subpanels |
| 6 AWG | 55 amps | 50 to 55 amp | Ranges, hot tubs, larger subpanel feeders |
How to Read This Chart
The 60 Degrees Celsius Rule
The conductors inside modern NM-B cable are insulated to 90 degrees Celsius, but NEC 334.80 limits the usable ampacity of NM cable to the 60 degrees Celsius column of Table 310.16. That is why 12 AWG copper Romex is held to 20 amps even though the same copper conductor in conduit could carry more.
Two-Wire vs Three-Wire
The gauge sets the amperage. Whether you need two conductors or three depends on the load. A 240-volt water heater uses 10/2, while a 30-amp dryer that needs a neutral uses 10/3. Choose the gauge by amps first, then the conductor count by the load.
When to Step Up a Gauge
Long cable runs can suffer voltage drop, and bundling multiple cables together or high ambient temperatures can require derating. In those cases an electrician may step up to a larger gauge. For a deeper breakdown including conduit conductors, derating, and voltage drop, see our full wire size chart.
Code and Safety Note
This chart covers common copper NM-B residential branch circuits and is a starting reference, not a substitute for a load calculation. Follow the National Electrical Code and local amendments, confirm with your authority having jurisdiction, and use a licensed electrician for new circuits and panel work.
IB Lighting stocks Southwire wire in every common gauge inside our electrical wire and cable collection, with free freight plus free freight insurance on every order. Call (800) 674-9019 if you are unsure which gauge your circuit needs.