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Size the run, not just the panel.

Enter the load, the distance, and the voltage — we'll give you the wire gauge that carries the load and keeps voltage drop in spec, copper or aluminum.

Load current

One-way distance (ft)

System voltage

Conductor

Phase

Max voltage drop 3%

NEC recommends ≤3% on a branch circuit (≤5% total feeder + branch).

Voltage drop by wire size

Wire	Ampacity	Drop	%

Voltage-drop estimate (VD = K·I·L·factor ÷ circular mils; K≈12.9 Cu / 21.2 Al, factor 2 for 1Ø, √3 for 3Ø). Ampacity is the 75°C column (THWN). For job-ready sizing also account for terminations, derating, ambient, and conduit fill — this is a planning aid, not a substitute for the NEC or your AHJ.

WattWorks quotes, explains, and books the job — so the estimate writes itself.

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