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What Size Wire for 70 Amps?

For 70 amps with the displayed 75 C termination defaults, start with 4 AWG copper or 3 AWG aluminum. This first feeder/subpanel page is where 60 A appliance logic stops being a safe shortcut.
Load
70 A
Distance
0 ft entered
Band
Feeder / subpanel
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
Copper4 AWG70 A85 ATermination rated 75 CPasses defaults
Aluminum3 AWG70 A75 ATermination rated 75 CPasses defaults
What Size Wire for 70 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 70 A ChangesAt 70 A, the page changes both the conductor size and the design conversation. The rendered defaults pass on termination-limited ampacity, but feeder length, neutral/ground separation, raceway fill, and load calculation are now central checks rather than side notes.

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
60 A6 AWG60 A4 AWG60 A
70 A (this page)4 AWG70 A3 AWG70 A
80 A4 AWG80 A2 AWG80 A
Copper and aluminum starting sizes for 70 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.

70 A Opens the Feeder/Subpanel Band

Feeder / subpanel context for a 70 A circuit.

A 70 A wire-size search is usually about a garage subpanel, shop feeder, larger equipment feeder, or a planned capacity step above a 60 A circuit. The job is less likely to be a simple appliance branch and more likely to involve a load calculation and feeder wiring method.

Under the displayed 75 C termination defaults, 70 A jumps from 6 AWG copper at 60 A to 4 AWG copper, and from 4 AWG aluminum to 3 AWG aluminum. The next 80 A page keeps copper at 4 AWG but moves aluminum again, so material choice becomes more visible.

What Changes This Answer

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

  • Do the feeder load calculation first

    A 70 A conductor answer assumes 70 A is the correct feeder or equipment rating. Confirm the load before selecting wire from the breaker size alone.

  • Do not extend 60 A habits upward

    Under these defaults, 60 A uses 6 AWG copper and 4 AWG aluminum. The 70 A page moves both materials larger.

  • Plan the full feeder, not only hot conductors

    Subpanels need the correct ungrounded conductors, neutral, equipment grounding conductor, enclosure bonding and termination listings for the selected material.

  • Check the terminal temperature marking

    The direct answer assumes 75 C terminations. If either end is limited to 60 C, rerun the calculator before relying on the displayed aluminum result.

  • Check the 80 A aluminum step

    Copper stays 4 AWG at 80 A under these defaults, while aluminum moves from 3 AWG to 2 AWG. Compare before changing the planned feeder rating.

70 Amp Wire Size FAQs

What size wire for 70 amps?
Under the 75 C termination defaults on this page, start with 4 AWG copper or 3 AWG aluminum. The displayed rows are governed by the 75 C termination path.
Can I use 60 A wire for a 70 A feeder?
No under these defaults. The 60 A page shows 6 AWG copper and 4 AWG aluminum, while 70 A moves to 4 AWG copper and 3 AWG aluminum.
Is 70 A a subpanel size or an appliance size?
It can be either, but this page treats it as the first feeder/subpanel band because many 70 A searches involve garage, shop or equipment feeders rather than ordinary appliance branches.
Why compare 70 A with 80 A?
Because the copper result stays on a plateau under these defaults while aluminum changes. The comparison helps show whether a planned rating change affects only the breaker or also the conductor material choice.