Wire Size Calculator
Find the recommended wire gauge (AWG) for your load based on NEC ampacity tables and voltage drop limits.
Recommended AWG
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NEC Ampacity
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Voltage Drop
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Drop %
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NEC Ampacity Reference (75C, Table 310.16)
| AWG | 14 | 12 | 10 | 8 | 6 | 4 | 3 | 2 | 1 | 1/0 | 2/0 | 3/0 | 4/0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cu (A) | 15 | 20 | 30 | 40 | 55 | 70 | 85 | 95 | 110 | 125 | 145 | 165 | 195 |
| Al (A) | - | 15 | 25 | 30 | 40 | 55 | 65 | 75 | 85 | 100 | 115 | 130 | 150 |
How this was calculated
Ampacity: NEC Table 310.16 at 75C insulation rating. Wire selected must have ampacity >= load.
Voltage drop: Vd = 2 x L x I x R/1000 (single-phase) or 1.732 x L x I x R/1000 (3-phase). Target: under 3%.
If voltage drop exceeds 3%, the next larger wire is recommended.
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Book a free strategy call →Wire Sizing Basics
Proper wire sizing prevents overheating, fire hazards, and excessive voltage drop. NEC (National Electrical Code) Table 310.16 provides ampacity ratings for copper and aluminum conductors. For long runs, voltage drop becomes the limiting factor: NEC recommends no more than 3% drop for branch circuits and 5% total. Always derate for ambient temperature, conduit fill, and continuous loads (multiply by 1.25). Built by Groundwork Analytics.