Skip to content
ElectraKit
Open menu

What Size Wire for 90 Amps?

For 90 amps with the displayed 75 C termination defaults, start with 3 AWG copper or 2 AWG aluminum. This page is the 80-to-90 A copper step before the 100 A aluminum jump.
Load
90 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
Copper3 AWG90 A100 ATermination rated 75 CPasses defaults
Aluminum2 AWG90 A90 ATermination rated 75 CPasses defaults
What Size Wire for 90 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 90 A ChangesAt 90 A, copper is the material that changes from the previous page. Aluminum stays 2 AWG and has no displayed margin above 90 A usable ampacity, so terminal rating and derating deserve an early check.

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
80 A4 AWG80 A2 AWG80 A
90 A (this page)3 AWG90 A2 AWG90 A
100 A3 AWG100 A1 AWG100 A
Copper and aluminum starting sizes for 90 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.

90 A Is the Copper Step in the Feeder Band

Feeder / subpanel context for a 90 A circuit.

A 90 A wire-size search usually means the planned feeder rating sits between common 80 A and 100 A decisions: shop panels, garage subfeeds, equipment feeders, or load-managed additions.

Under the displayed 75 C termination defaults, copper moves from 4 AWG at 80 A to 3 AWG here, while aluminum stays 2 AWG. The next 100 A page keeps copper at 3 AWG but moves aluminum to 1 AWG.

What Changes This Answer

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

  • Do not keep the 80 A copper answer

    Under these defaults, 80 A copper is 4 AWG, while 90 A copper moves to 3 AWG.

  • Watch aluminum margin

    The 2 AWG aluminum row shows 90 A usable ampacity under 75 C terminations. Hot ambient, bundling, or 60 C terminals can force a larger conductor.

  • Compare 100 A before standardizing

    The adjacent 100 A page keeps copper at 3 AWG but moves aluminum from 2 AWG to 1 AWG.

  • Treat this as feeder planning

    Subpanels and equipment feeders also need load calculation, neutral and grounding conductor sizing, raceway fill, lug listing, and voltage drop checks.

90 Amp Wire Size FAQs

What size wire for 90 amps?
Under the 75 C termination defaults on this page, start with 3 AWG copper or 2 AWG aluminum. The aluminum row has no extra displayed ampacity above 90 A.
Why does copper change at 90 A?
The 80 A page uses 4 AWG copper under these defaults. At 90 A, copper moves to 3 AWG while aluminum remains 2 AWG.
Is 90 A close enough to use a 100 A answer?
Use the page matching the actual overcurrent device and load calculation. Copper matches 100 A under these defaults, but aluminum changes at 100 A.
Can 2 AWG aluminum be used for every 90 A feeder?
No. The displayed result assumes 75 C terminations and the page defaults. Listed aluminum lugs, derating, distance, and 60 C equipment can change the answer.