WireGaugeCalc Free calculator · NEC cited · works offline
Electical Wire Size
electical wire size is fast with WireGaugeCalc, since you enter the load amps and the tool reads the NEC 310.16 ampacity table for you.
It checks copper or aluminum and the 60, 75, or 90 degree C termination column so the answer matches the lugs on your breaker and device.
You get a clear AWG or kcmil result in seconds, so you can pull the right conductor the first time.
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.
How to Size Wire Against the NEC 310.16 Table
The calculator compares your circuit load to the rated ampacity for each gauge, so the conductor never carries more current than its insulation allows.
It defaults to the 75 degree C column because most breakers and lugs are rated for 75 degree C terminations.
Switch the conductor material to aluminum and the result steps up a size, since aluminum carries less current per gauge than copper.
What Drives the Electical Wire Size Result
A few inputs change the gauge you need:
- Load in amps from the breaker or the connected equipment
- Conductor material, copper or aluminum
- Termination temperature column, 60, 75, or 90 degree C
- Number of current-carrying conductors for derating
- Ambient temperature where the run is installed
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 use the 75 degree C column by default?
Most breakers, panels, and device lugs are rated for 75 degree C terminations, so sizing to that column keeps the connection within its rating. Always confirm the temperature stamped on the equipment and verify against the current NEC and your local authority having jurisdiction.
How do I know whether to pick copper or aluminum?
Pick the material your installation actually uses, since aluminum needs a larger gauge for the same load. The tool steps the result up automatically when you choose aluminum.
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.