WireGaugeCalc Free calculator · NEC cited · works offline
Wire Size For 20 Amp
Wire size for 20 amp circuits is quick to confirm with WireGaugeCalc, since the calculator reads the NEC 310.16 ampacity table for you.
You choose copper or aluminum and the termination temperature, so the gauge matches the breaker and the device terminals.
You get the minimum size at once, so you can run the right conductor without second guessing.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
20 Amp Circuit Wire Size
The 20 amp wire size is normally 12 AWG copper, since 12 AWG copper carries 20 amps at the 60 degree C column used for branch circuits.
10 AWG aluminum is the common match when you choose aluminum.
The calculator verifies the gauge against the table, so the 20 amp wire gauge is correct before you pull it.
Gauge Of Wire For A 20 Amp Circuit
A few inputs set the result:
- Conductor material, since copper at 12 AWG meets 20 amps directly
- Termination temperature, usually 60 degrees C for standard receptacles
- The 20 amp breaker rating the conductor must carry
- Whether the load is continuous, which can push the size up
- The 20 amp outlet wire size that matches the device terminals
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 I use 14 AWG on a 20 amp breaker?
No, 14 AWG is limited to 15 amps and is not allowed on a 20 amp breaker. Use 12 AWG copper for a 20 amp circuit.
What is the 20 amp outlet wire size for copper?
A 20 amp receptacle circuit uses 12 AWG copper conductors. Verify the size against the current NEC and your local authority having jurisdiction before wiring.
Does a long run change the 20 amp wire size?
A long run can call for 10 AWG copper to keep voltage drop within about 3 percent on the branch circuit. The calculator flags this when you enter the distance.
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.