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What Size Wire for 30 Amps?

For a non-continuous 30 amp load under the default short-run assumptions, start with 10 AWG copper or 8 AWG aluminum. This is the top of the small-conductor branch-circuit band.
Load
30 A
Distance
0 ft entered
Band
Branch circuit
Defaults
Non-continuous, 75 C lugs, 86 F, 240 V single-phase
Conductor count
3 current-carrying

Computed Starting Point

The table uses common defaults. Change the calculator inputs for the actual installation.

MaterialComputed sizeOCPDUsable ampacityGoverning constraintDefault check
Copper10 AWG30 A30 ASmall conductor overcurrent limitPasses defaults
Aluminum8 AWG30 A40 ATermination rated 75 CPasses defaults
What Size Wire for 30 Amps? under common non-continuous defaults: THHN or XHHW-2 insulation, 75 C terminations, 86 F ambient, 240 V single-phase, no more than three current-carrying conductors, and 0 ft route length entered.

What 30 A ChangesAt 30 A, the page is the upper edge of the small branch-circuit range. Copper is still 10 AWG under the small-conductor limit, but aluminum has already moved to 8 AWG and termination ampacity becomes the displayed constraint.

Run the wire size calculator

Adjacent Amp Ratings

See whether stepping one standard size up or down forces a conductor jump under the same defaults.

LoadCopper sizeCopper OCPDAluminum sizeAluminum OCPD
25 A10 AWG25 A10 AWG25 A
30 A (this page)10 AWG30 A8 AWG30 A
40 A8 AWG40 A8 AWG40 A
Copper and aluminum starting sizes for 30 A and the neighboring published amp pages, under the same defaults as the result above.

A plateau means neighboring amp ratings share a conductor size under these defaults. A jump means a standard breaker change often needs a larger wire; confirm with your real ambient, length and terminations.

30 A Is the Small-Conductor Ceiling

Branch circuit context for a 30 A circuit.

A 30 A wire-size search usually points to a dryer, water heater, RV receptacle, small welder, listed appliance, or a dedicated equipment branch. It is common enough to feel simple, but equipment instructions still decide many real installations.

Under the non-continuous defaults, copper stays at 10 AWG from the 25 A page to 30 A, while aluminum moves from 10 AWG at 25 A to 8 AWG here. The next published amp page, 40 A, moves copper up to 8 AWG too.

What Changes This Answer

Checks that can change the starting conductor under the displayed defaults.

  • Do not borrow the 25 A aluminum answer

    Under these defaults, 25 A aluminum is 10 AWG, while 30 A aluminum moves to 8 AWG.

  • Check appliance instructions

    Dryers, water heaters, RV receptacles and listed equipment can have equipment-specific circuit requirements. Use the nameplate where it is more specific.

  • Compare 40 A before upsizing the breaker

    The adjacent 40 A page moves copper to 8 AWG under the same defaults. Do not change breaker size without a load and equipment basis.

  • Use continuous and distance inputs when needed

    This amp-only answer assumes a non-continuous load and no route length. Continuous loads or long 120 V or 240 V paths should be checked with the calculator.

  • Use listed aluminum terminations

    The aluminum row is a calculator output for listed aluminum terminations. Do not use aluminum equipment or devices unless they are listed for it.

30 Amp Wire Size FAQs

What size wire for 30 amps?
Under the non-continuous defaults on this page, start with 10 AWG copper or 8 AWG aluminum. The copper result is small-conductor governed, while aluminum is termination-governed and needs listed aluminum terminations.
Is 30 A the same wire size as 25 A?
Copper matches at 10 AWG under these defaults, but aluminum does not. The 25 A page shows 10 AWG aluminum, while 30 A moves to 8 AWG aluminum.
Can I use 10 AWG copper for 40 amps?
Not under these defaults. The 40 A page moves copper to 8 AWG.
Should a dryer or RV outlet always use this answer?
No. Treat this as the calculator default starting point, then follow the actual equipment nameplate, receptacle rating, route length and local review.