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What Size Wire for 15 Amps?

For a non-continuous 15 amp load under the default short-run assumptions, start with 14 AWG copper. The calculator also shows 12 AWG aluminum when listed aluminum terminations are available, but aluminum is uncommon on small branch circuits.
Load
15 A
Distance
0 ft entered
Band
Branch circuit
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
Copper14 AWG15 A15 ASmall conductor overcurrent limitPasses defaults
Aluminum12 AWG15 A15 ASmall conductor overcurrent limitPasses defaults
What Size Wire for 15 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 15 A ChangesAt 15 A, the non-continuous default copper result is 14 AWG, protected at 15 A. The aluminum row is a calculator output for listed aluminum terminations, not the usual small branch-circuit choice; using a larger conductor does not turn the circuit into 20 A.

Run the wire size calculator

Adjacent Amp Ratings

Compare the next published amp rating under the same defaults.

LoadCopper sizeCopper OCPDAluminum sizeAluminum OCPD
15 A (this page)14 AWG15 A12 AWG15 A
20 A12 AWG20 A10 AWG20 A
Copper and aluminum starting sizes for 15 A and the next published amp page, 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.

15 A Is the Small Branch-Circuit Floor

Branch circuit context for a 15 A circuit.

A 15 A wire-size search is usually about ordinary lighting, receptacles, controls, fans, garage-door openers, or a small dedicated load. The user often wants to know whether 14 AWG copper is still the right starting point.

Under the non-continuous defaults on this page, 15 A is governed by the small-conductor overcurrent limit. There is no lower adjacent amp page here, so the useful comparison is upward: 20 A moves to a different conductor set.

What Changes This Answer

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

  • Do not carry 15 A logic to 20 A

    The adjacent 20 A page moves to 12 AWG copper or 10 AWG aluminum under the same defaults.

  • Check actual load type

    Lighting, receptacles and dedicated equipment can have different listing or nameplate requirements. Use the equipment instructions when they are more specific.

  • Watch long 120 V runs

    The amp-only page assumes no distance. A long 120 V branch circuit should be checked in the calculator for voltage drop.

  • Rerun continuous loads

    The displayed answer does not apply the 125 percent continuous-load multiplier. If the load runs three hours or more, use the calculator's continuous setting.

  • Treat aluminum as uncommon here

    Aluminum is not typical for small branch circuits. If it is used, both the conductor size and terminations must support aluminum.

15 Amp Wire Size FAQs

What size wire for 15 amps?
Under the non-continuous defaults on this page, start with 14 AWG copper. The calculator also shows 12 AWG aluminum with a 15 A overcurrent device, but only use aluminum where the equipment is listed for it.
Can I use 14 AWG copper on a 20 A breaker?
Not under the small-conductor limit used by this page. The 20 A page moves to 12 AWG copper under the same defaults.
Does larger wire make a 15 A circuit into 20 A?
No. The breaker or fuse still limits the circuit. A larger conductor may be used for other reasons, but it does not authorize a larger overcurrent device by itself.
When should I use the calculator instead of this page?
Use the calculator for long runs, high ambient temperature, bundled conductors, continuous loads, or equipment instructions that differ from the page defaults.