Wire Gauge Calculator
NewCalculate the minimum recommended copper wire gauge (AWG) for a circuit based on current, run length, voltage, and acceptable voltage drop.
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recommended minimum wire gauge (AWG)
Based on copper wire voltage-drop calculations, not NEC ampacity tables. Always verify against local electrical code and consult a licensed electrician for actual installations.
Frequently Asked Questions
What is voltage drop, and why does it matter?
Voltage drop is the reduction in voltage that occurs as current travels through a wire's resistance over distance — excessive voltage drop can cause dim lighting, reduced motor performance, and inefficient power delivery, which is why electrical codes recommend keeping it under a specific percentage of the circuit's rated voltage.
Why does the calculator double the run length?
Current has to travel out to the load and back to the source to complete the circuit, so the calculator uses round-trip wire length (2 × the one-way distance) when computing total resistance, since both the "hot" and "neutral/return" conductors contribute resistance to the voltage drop.
What's the difference between the two circuit type options?
"General purpose" uses a 3% maximum voltage drop, the commonly cited NEC recommendation for typical branch circuits, while "sensitive equipment" uses a stricter 1% limit for circuits feeding voltage-sensitive electronics where even small drops can affect performance.
Does this replace official ampacity tables?
No — this tool calculates the minimum gauge needed to keep voltage drop within your chosen limit, which is a separate consideration from a wire's safe current-carrying capacity (ampacity) defined in NEC tables. Always cross-check against your local electrical code's ampacity requirements and consult a licensed electrician for actual installations.