WireGaugeCalc Free calculator · NEC cited · works offline
Sizing Gauge For Current
Sizing gauge for current is fast with WireGaugeCalc, since you enter the load amps and the calculator returns the smallest conductor that carries it safely.
It reads the NEC 310.16 ampacity table for your conductor material and termination temperature, so the gauge it picks matches the column your breaker and lugs actually use.
You get a defensible wire size in seconds instead of counting rows by hand.
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.
Match The Gauge To The Load And The Termination Temp
Enter the continuous and noncontinuous load, and the calculator applies the 125% factor where it belongs so the conductor is not undersized.
It checks copper or aluminum against the 60, 75, or 90 degree C column, since the rating of your terminations sets which ampacity you may use.
What Goes Into The Wire Gauge Result
A few inputs drive the gauge the calculator returns:
- Load current in amps, with continuous loads bumped by 125%
- Conductor material, copper or aluminum
- Termination temperature column: 60, 75, or 90 degrees C
- Ambient temperature and conductor count for any derating
- The NEC 310.16 ampacity row that first meets the demand
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
Why does the calculator ask for termination temperature?
Because NEC 110.14(C) ties your usable ampacity to the lowest-rated termination in the circuit. Most 75 degree lugs mean you size from the 75 degree column even if the wire is rated 90 degrees.
Does the gauge change for aluminum versus copper?
Yes, aluminum has lower ampacity per size, so it usually steps up at least one gauge for the same current. Confirm the final size against the current NEC and your local authority having jurisdiction.
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.