Skip to content
ElectraKit
Open menu

What Size Wire for 100 Amps at 100 Feet?

At 100 ft, a 100 A feeder still lands on the ampacity-only starting sizes under these defaults: 3 AWG copper or 1 AWG aluminum. The next published length is where drop starts changing the answer.
Load
100 A
Distance
100 ft
Band
100 A feeder
Defaults
Non-continuous, 75 C lugs, 86 F, 240 V single-phase

Computed Starting Point

Ampacity and voltage drop under common defaults for this amp and distance.

MaterialComputed sizeOCPDUsable ampacityGoverning constraintDefault check
Copper3 AWG100 A100 ATermination rated 75 CPasses defaults
Aluminum1 AWG100 A100 ATermination rated 75 CPasses defaults
What Size Wire for 100 Amps at 100 Feet? under common non-continuous defaults: THHN or XHHW-2 insulation, 75 C terminations, 86 F ambient, 240 V single-phase and no more than three current-carrying conductors.

What 100 ft ChangesUnder the default 240 V, noncontinuous 100 A setup, 100 ft does not upsize the conductor from the ampacity-only result. Termination ampacity still governs, but a slightly longer measured route, continuous loading, hotter ambient, or 120 V load can move the job into the voltage-drop pages immediately above it.

Run the wire size calculatorCheck voltage drop alone

Zero-Length vs This Distance

If the distance-adjusted size is larger, voltage drop governed under these defaults.

CaseCopper sizeCopper constraintAluminum sizeAluminum constraint
Ampacity only (0 ft)3 AWGTermination rated 75 C1 AWGTermination rated 75 C
100 ft (this page)3 AWGTermination rated 75 C1 AWGTermination rated 75 C
Copper and aluminum sizes for 100 A with no distance entered versus 100 ft one-way.

Adjacent Distances at This Amp

Neighboring published lengths for 100 A under the same defaults.

DistanceCopper sizeAluminum sizeCopper constraint
100 ft (this page)3 AWG1 AWGTermination rated 75 C
150 ft2 AWG1/0 AWGVoltage drop
100 A copper and aluminum starting sizes across neighboring distance pages.

100 ft Is the Short Outbuilding Edge

100 A feeder context for 100 A at 100 ft.

A 100 ft 100 A search is usually a garage, small shop, ADU, or short detached-building feeder where the user wants to know whether the ordinary 100 A conductor still survives once route length is included.

Under the defaults on this page, the zero-length row and the 100 ft row match. That makes this page a boundary check: the route is long enough to ask about drop, but not long enough in this model to change the computed conductor.

What Changes This Long-Run Answer

Checks that matter for distance-governed sizing in this amp band.

  • Do not round a longer route down

    The one-way conductor path includes bends, vertical drops, panel location and trench detours. A route that measures closer to 130-150 ft belongs in the next distance check.

  • Use 100 ft as a boundary check

    Because the zero-length and 100 ft rows match under these defaults, this page tells you drop has not yet beaten ampacity for this exact setup.

  • Confirm the load is not continuous

    A feeder carrying EVSE or another sustained load can need 125 percent sizing before this 100 A answer is even the right input.

  • Keep the 150 ft jump visible

    The adjacent table shows the next published length. If the route grows, copper and aluminum both move to larger conductors under the same assumptions.

100 A at 100 ft FAQs

Does 100 ft require larger wire for 100 amps?
Not under the defaults used on this page. The computed 100 ft result matches the zero-length ampacity result: 3 AWG copper or 1 AWG aluminum.
Why does 150 ft use larger wire than 100 ft?
In this model, 150 ft is where voltage drop becomes the governing constraint for the published 100 A distance set. That is why the neighboring page jumps to larger conductors.
Can I use aluminum for a 100 A feeder at 100 ft?
Often yes when the lugs are listed for aluminum and the route matches the defaults. Confirm material, termination temperature, torque requirements and the actual one-way length.