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What Size Breaker for 4 AWG Wire?

For 4 AWG wire under the displayed non-receptacle defaults, the largest common breaker is 90 A for copper and 70 A for aluminum. This is the last mid-branch page before the series moves into large feeder wire sizes.
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4 AWG
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Compatibility calculator

Breaker Starting Point

Maximum common breaker sizes under common conditions. Derating or receptacle limits can reduce these.

MaterialConductorLargest common breakerAssumptions
Copper4 AWG copper90 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
Aluminum4 AWG aluminum70 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
What Size Breaker for 4 AWG Wire? under common non-receptacle defaults: 90 C insulation, 75 C lugs, 86 F ambient, no more than three current-carrying conductors, and next-size-up checks only where eligible.

What 4 AWG ChangesAt 4 AWG, the page is a feeder-planning boundary. The displayed 90 A copper and 70 A aluminum maximums depend on the non-receptacle next-size-up default, and the next published 3 AWG page moves into the large-feeder band.

Check breaker and wire together

Adjacent Wire Sizes

See whether stepping one conductor size changes the maximum standard breaker.

WireCopper max breakerAluminum max breaker
6 AWG70 A50 A
4 AWG (this page)90 A70 A
3 AWG100 A80 A
Largest common breakers for 4 AWG and neighboring published wire sizes under the same defaults.

4 AWG Is the Last Mid-Branch Step

Mid branch / appliance context for 4 AWG wire.

A 4 AWG breaker-size search often points to a larger equipment feeder, subpanel, shop circuit, or a planned step above common 60 A work. At this size, voltage drop, lug range, and load calculation are no longer side notes.

Under the displayed defaults, 4 AWG copper reaches a 90 A maximum breaker and 4 AWG aluminum reaches 70 A. Both results lean on the non-receptacle next-size-up path because the 75 C ampacity values sit between standard breaker ratings.

Field Checks for This Wire Size

Checks that matter in this conductor band — not a generic breaker list.

  • Do not reuse 6 AWG answers

    Under these defaults, 6 AWG copper returns 70 A and 6 AWG aluminum returns 50 A. This 4 AWG page moves both materials larger.

  • Check next-size-up eligibility

    The displayed 90 A copper and 70 A aluminum maximums depend on the non-receptacle next-size-up default. Confirm the circuit type before rounding above usable ampacity.

  • Plan lugs and raceway

    Subpanels, disconnects, and equipment lugs must accept 4 AWG in the chosen material. Raceway fill and bending space can also drive the final design.

  • Run load and voltage-drop checks

    A breaker maximum only protects the conductor. Long feeders and calculated loads can require a larger conductor even when the breaker compatibility table passes.

4 AWG Breaker FAQs

What size breaker for 4 AWG wire?
Under the displayed non-receptacle defaults on this page, 4 AWG copper has a 90 A maximum breaker and 4 AWG aluminum has a 70 A maximum breaker.
Why does 4 AWG copper show 90 A?
The 75 C ampacity path lands between standard breaker ratings. With the page's non-receptacle default, the next-size-up path reaches 90 A.
Can 4 AWG aluminum use a 90 A breaker?
No under these defaults. The 90 A result belongs to copper. The 4 AWG aluminum row returns a 70 A maximum breaker.
Should I use the 3 AWG page instead?
Only when the load calculation, equipment rating, conductor material, terminal temperature, and circuit type support moving into the next large-feeder step.
Can I use this page as final approval for a 4 AWG feeder?
No. Treat it as a compatibility starting point only. Feeder work still needs load calculation, terminal temperature, conductor material, raceway fill, voltage drop, equipment listings, and AHJ review.