Wire Gauge Calculator
Enter circuit amperage, one-way wire run distance, and voltage to get the NEC-compliant minimum wire gauge, actual voltage drop percentage, and whether you need to upsize for the voltage drop limit.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
What gauge wire do I need for a 20-amp circuit?
A 20-amp circuit requires 12 AWG copper wire minimum per NEC code. If the run is longer than about 75 feet on 120V, check whether the voltage drop exceeds 3% — if so, upsize to 10 AWG.
Can I use aluminum wire for branch circuits?
Aluminum wire is not recommended for branch circuits under 60A because connections at receptacles and switches are rated for copper only. Aluminum is appropriate for service entrance conductors and larger feeders (60A+) where all terminations are rated for aluminum (AL/CU rated).