Wire Gauge Ampacity Calculator
Safe current rating for common copper wire gauges.
Enter your values
ⓘ Live results
Results
- Rated ampacity (60°C copper)
- 20 A
- Recommended max continuous load (80%)
- 16 A
- Wire gauge
- 12 AWG
Quick answer
Ampacity depends on wire gauge, insulation type and installation conditions.
Lookup by AWG (60C copper, NEC Table 310.16 style)
How to use the Wire Gauge Ampacity Calculator
- 1Choose the copper wire gauge you are working with.
- 2Read the standard ampacity rating for general-purpose 60C insulation.
- 3Apply the 80% continuous-load derating used in most electrical codes.
Worked example
Using the values the calculator loads with:
Inputs
- Wire gauge (AWG)12 AWG
Results
- Rated ampacity (60°C copper)20 A
- Recommended max continuous load (80%)16 A
- Wire gauge12 AWG
Frequently asked questions
Why derate to 80%?
Continuous loads run for 3+ hours and codes require sizing at 80% of the breaker/wire rating to prevent overheating.
Does insulation type matter?
Yes, 75C and 90C rated insulation allow higher ampacities on the same gauge; check your local code table.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.