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What Size Wire for 225 Amps?

For 225 amps with the displayed 75 C termination defaults, start with 4/0 AWG copper or 300 kcmil aluminum. This page sits above the common 200 A service decision and has tight 75 C margins for both materials.
Load
225 A
Distance
0 ft entered
Band
Service / large feeder
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
Copper4/0 AWG225 A230 ATermination rated 75 CPasses defaults
Aluminum300 kcmil225 A230 ATermination rated 75 CPasses defaults
What Size Wire for 225 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 225 A ChangesAt 225 A, both displayed rows show only 230 A usable ampacity under the 75 C defaults. Equipment limited to 60 C will force larger conductors, and even modest derating or product constraints can move the final size.

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
200 A3/0 AWG200 A250 kcmil200 A
225 A (this page)4/0 AWG225 A300 kcmil225 A
250 A250 kcmil250 A350 kcmil250 A
Copper and aluminum starting sizes for 225 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.

225 A Is the Step Above a 200 A Service

Service / large feeder context for a 225 A circuit.

A 225 A wire-size search usually points to a larger panelboard, service-equipment step above 200 A, shop feeder, multi-load feeder, or light commercial-style service conversation. It is no longer the common residential 200 A shortcut; equipment lugs, conductor product, and available fault and service coordination become more visible.

Under the displayed 75 C termination defaults, copper moves from 3/0 AWG at 200 A to 4/0 AWG here, while aluminum moves from 250 kcmil to 300 kcmil. The next 250 A page changes both materials again, so 225 A is a narrow rating with little displayed ampacity margin.

What Changes This Answer

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

  • Do not reuse 200 A conductors

    Under these defaults, 200 A uses 3/0 AWG copper and 250 kcmil aluminum. This 225 A page moves to 4/0 AWG copper and 300 kcmil aluminum.

  • Watch the 230 A displayed margin

    Both materials show 230 A usable ampacity under the displayed 75 C defaults. Hot ambient, bundling, product limits, or longer runs can remove that small margin.

  • Check 60 C equipment limits

    The displayed 4/0 AWG copper and 300 kcmil aluminum results are 75 C defaults. Equipment limited to 60 C will force larger conductors for a full 225 A feeder or service.

  • Compare 250 A before upsizing

    The adjacent 250 A page moves copper to 250 kcmil and aluminum to 350 kcmil under the same defaults. Do not change the planned rating without load and equipment support.

  • Confirm equipment lugs and raceway

    Large conductors need compatible lugs, bending space, raceway fill, grounding and bonding checks, and utility or AHJ coordination.

225 Amp Wire Size FAQs

What size wire for 225 amps?
Under the 75 C non-continuous defaults on this page, start with 4/0 AWG copper or 300 kcmil aluminum. Confirm terminal ratings, conductor product, load calculation, raceway fill, and utility or AHJ requirements.
Is 225 A the same wire size as 200 A?
No under these defaults. The 200 A page shows 3/0 AWG copper and 250 kcmil aluminum, while 225 A moves to 4/0 AWG copper and 300 kcmil aluminum.
Why is the 225 A margin tight?
Both displayed rows show 230 A usable ampacity under 75 C defaults. That passes the default check but leaves little room for 60 C equipment, derating, or product constraints.
Should I jump from 225 A to 250 A?
Only when the load calculation, service equipment, overcurrent device, and utility or AHJ requirements support 250 A. The adjacent 250 A page uses larger conductors.
Can I use this page as final approval for a 225 A feeder?
No. Treat it as a planning starting point only. Large feeders still need conductor product verification, equipment lug checks, raceway fill, grounding and bonding, utility or AHJ review, and a load calculation.