Wire Gauge Ampacity Calculator — Free Online Calculator & Guide
Find the correct AWG wire gauge for any electrical circuit based on current, conductor material, insulation rating, and conduit fill.
✓ Formula verified: January 2026
Wire Gauge
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Recommended Wire Gauge
12 AWG (copper) — 20A rated
Design Current (after derating)
20.0 A
Derating Factor Applied
▲ 100%
What if your circuit current (amperes) changes? 18 A → 12 AWG (copper) — 20A rated · 20 A → 12 AWG (copper) — 20A rated · 22 A → 10 AWG (copper) — 30A rated
Scenario Comparison
Conservative (5%)
$16,470.09
$6,470.09 interest
Your scenario (7%)
$20,096.61
$10,096.61 interest
Aggressive (10%)
$27,070.41
$17,070.41 interest
High-risk (14%)
$40,224.71
$30,224.71 interest
Best return
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Wire Gauge
Recommended Wire
12 AWG (copper) — 20A rated
Design Current20.0 A
Derating Factor100%
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