WireGaugeCalc Free calculator · NEC cited · works offline
Max Amps For 12 Gauge Wire
max amps for 12 gauge wire is quick to check with WireGaugeCalc, since the app reads the 310.16 ampacity columns.
You pick copper or aluminum and the termination temperature, so the calculator returns the current 12 AWG can carry.
That tells you which breaker the conductor supports.
Open the calculatorAllowable ampacity from NEC Table 310.16 at the chosen termination temperature. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Ampacity Of 12 AWG By Termination Column
12 AWG copper is rated for 25 amps in the 90 degree C column, but it is commonly protected at 20 amps for general use.
The breaker follows the lowest rated terminal, so the 75 degree C value of 25 amps still defers to the 20 amp limit set by 240.4(D).
Aluminum 12 AWG carries less, so the calculator shows its lower rating in the same view.
12 AWG 120V Wire Max Overcurrent Protection
Several rules set the breaker for 12 gauge wire:
- Copper 12 AWG is generally limited to a 20 amp breaker
- NEC 240.4(D) caps small conductors regardless of column rating
- Termination temperature still applies to the conductor lookup
- Continuous loads use the 125 percent factor
- Derating for heat or fill can lower the usable ampacity
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Can 12 gauge copper wire handle 25 amps?
The 90 degree C column rates 12 AWG copper at 25 amps, but NEC 240.4(D) usually limits the breaker to 20 amps for general circuits. Check the current NEC and your local authority having jurisdiction before using a larger device.
What breaker goes with 12 AWG copper?
A 20 amp breaker is the standard match for 12 AWG copper on a 120V branch circuit. The calculator confirms the max overcurrent protection for your inputs.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.