Enter Circuit Specs
Set your system voltage, current draw, and wire run distance. Select copper or aluminum and DC or AC.
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A wire gauge calculator determines the minimum AWG wire size for electrical circuits based on current, voltage, distance, and acceptable voltage drop. It covers both copper and aluminum conductors for AC and DC systems, with NEC ampacity verification to prevent fire hazards.
Circuit Parameters
Measure from panel/source to load
Wire Sizing Results
Voltage Drop
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Voltage at Load
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Power Loss
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NEC Ampacity
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How It Works
Voltage Drop Analysis
WireRight calculates the voltage drop for each AWG size using conductor resistance tables and your specific run length.
NEC Ampacity Check
Each gauge is checked against NEC Table 310.16 for maximum current capacity at 75°C insulation rating.
Size Your Wire
The recommendation picks the smallest gauge that meets BOTH your voltage drop target AND NEC ampacity requirements.
Why Wire Gauge Sizing Matters
Undersized wire causes voltage drop — your 12V battery delivers only 10.8V at the end of a long run, making lights dim and motors overheat. In extreme cases, undersized conductors cause fires. The National Electrical Code (NEC) limits voltage drop to 3% for branch circuits and 5% for feeders. For low-voltage DC systems (solar, RV, marine), wire sizing is even more critical because the lower voltage means higher current for the same wattage. WireRight calculates the minimum AWG gauge that satisfies both your voltage drop target and NEC ampacity limits — for copper or aluminum, DC or AC.
Frequently Asked Questions
How do you determine the correct wire gauge for a circuit?
Wire gauge depends on four factors: current (amps), voltage, one-way distance, and acceptable voltage drop percentage (typically 3% for branch circuits, 5% total). Higher current, longer distances, and lower voltage all require thicker (lower AWG number) wire. NEC ampacity tables set the absolute maximum current per gauge.
What is acceptable voltage drop for electrical wiring?
The National Electrical Code recommends no more than 3% voltage drop on any branch circuit and no more than 5% total (feeder + branch combined). For a 120V circuit, 3% means a maximum 3.6V drop. For 12V DC systems (solar, automotive), even 3% (0.36V) can be significant.
What is the difference between copper and aluminum wire sizing?
Aluminum wire has about 61% the conductivity of copper, so it requires a larger gauge for the same ampacity. For example, where copper uses 12 AWG, aluminum needs 10 AWG. Aluminum is lighter and cheaper per foot but requires special connectors rated for aluminum to prevent oxidation and fire risk.