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What Size Wire for 45 Amps?

For a non-continuous 45 amp load with the displayed 75 C termination defaults, start with 8 AWG copper or 6 AWG aluminum. This uncommon appliance-size page is mainly a nameplate and adjacent-rating check.
Load
45 A
Distance
0 ft entered
Band
Appliance / mid branch
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
Copper8 AWG45 A50 ATermination rated 75 CPasses defaults
Aluminum6 AWG45 A50 ATermination rated 75 CPasses defaults
What Size Wire for 45 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 45 A ChangesAt 45 A, the page is not a clean halfway point between 40 A and 50 A. Copper remains 8 AWG under the displayed defaults, but aluminum steps up to 6 AWG, so material choice drives the adjacent-rating difference.

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
40 A8 AWG40 A8 AWG40 A
45 A (this page)8 AWG45 A6 AWG45 A
50 A8 AWG50 A6 AWG50 A
Copper and aluminum starting sizes for 45 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.

45 A Is the Appliance Middle Step

Appliance / mid branch context for a 45 A circuit.

A 45 A wire-size search usually comes from equipment rather than a general-purpose branch circuit: cooking equipment, heaters, shop equipment, or a manufacturer-specified circuit.

Under the displayed 75 C termination defaults, copper stays at 8 AWG from 40 A to 45 A, while aluminum moves from 8 AWG to 6 AWG. That material split is the useful reason this page deserves its own answer.

What Changes This Answer

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

  • Start from equipment data

    A 45 A requirement is usually nameplate-driven. Use listed minimum circuit ampacity, terminal rating and maximum overcurrent protection when they are provided.

  • Do not reuse 40 A aluminum

    Under these defaults, 40 A aluminum is 8 AWG, while 45 A aluminum moves to 6 AWG.

  • Compare 50 A before rounding up

    Do not round a 45 A requirement to 50 A without equipment and load support. Adjacent pages are comparison tools, not permission to change ratings.

  • Check distance and continuous load

    This amp-only answer assumes a non-continuous load, 75 C terminations and no route length. Long runs, continuous loads or 60 C equipment should be rerun with actual inputs.

45 Amp Wire Size FAQs

What size wire for 45 amps?
Under the non-continuous 75 C termination defaults on this page, start with 8 AWG copper or 6 AWG aluminum. Confirm the equipment nameplate and terminal rating before treating that as a final answer.
Why does aluminum change at 45 A?
Under these defaults, aluminum moves from 8 AWG at 40 A to 6 AWG at 45 A, while copper remains 8 AWG.
Is 45 A the same as 40 A or 50 A wire size?
Under the displayed 75 C defaults, 45 A matches 50 A for the conductor labels: 8 AWG copper and 6 AWG aluminum. It does not match 40 A for aluminum, because 40 A shows 8 AWG aluminum while 45 A moves to 6 AWG.
Should I round a 45 A circuit to 50 A?
Only if the equipment instructions and load calculation support that rating. This page should not be used to change the required overcurrent device by guesswork.