WWireWise Tools

WIRE REFERENCE

Wire gauge &
ampacity guide

Quick reference for common conductor sizes. Always verify the insulation, terminals, installation conditions, equipment instructions, and locally adopted code before selecting wire.

COMMON BRANCH CIRCUITS

Fast copper reference

Common maximum overcurrent protection for general copper branch-circuit conductors, subject to NEC exceptions and all applicable conditions.

14 AWG15 ACommon lighting circuits
12 AWG20 ACommon receptacle circuits
10 AWG30 ACommon equipment circuits
8 AWG40–50 ADepends on the permitted temperature column
6 AWG55–65 ADepends on the permitted temperature column

75°C COLUMN

Common building-wire ampacity

For not more than three current-carrying conductors in a raceway, cable, or earth, based on a 30°C (86°F) ambient temperature. Use this column only when the conductor and every termination are permitted for 75°C.

Wire sizeCopperAluminum / copper-clad aluminum
14 AWG20 A*—
12 AWG25 A*20 A*
10 AWG35 A*30 A*
8 AWG50 A40 A
6 AWG65 A50 A
4 AWG85 A65 A
3 AWG100 A75 A
2 AWG115 A90 A
1 AWG130 A100 A
1/0 AWG150 A120 A
2/0 AWG175 A135 A
3/0 AWG200 A155 A
4/0 AWG230 A180 A

*Small-conductor rule: Unless specifically permitted otherwise, overcurrent protection is generally limited to 15 A for 14 AWG copper, 20 A for 12 AWG copper, and 30 A for 10 AWG copper. The table ampacity is not automatically the breaker size.

BEFORE YOU SIZE IT

Six checks that can change the answer

  1. Load: include continuous-load and equipment-specific sizing rules.
  2. Terminals: use the lowest permitted temperature rating in the circuit.
  3. Conductors: adjust when more than three current-carrying conductors share a raceway or cable.
  4. Heat: correct ampacity for ambient temperature and rooftop exposure when required.
  5. Distance: check voltage drop; ampacity alone may not produce acceptable performance.
  6. Location: confirm wet/dry rating, wiring method, conductor material, and local amendments.