WireGaugeCalc Free calculator · NEC cited · works offline
Ground Radial Wire Size
Ground radial wire size is fast with WireGaugeCalc, since you enter the expected current, run length, and conductor material and the tool returns the gauge.
It sizes the conductor against NEC 310.16 ampacity, so the radial carries current without overheating.
That gives you a defensible gauge before you trench the field.
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.
Sizing The Radial Conductor For Current
Ampacity comes from NEC 310.16, so the gauge matches the load and the termination temperature column.
Copper and aluminum carry current differently, so the calculator adjusts the size for the material you bury.
Long radial runs add resistance, so length factors into the gauge it recommends.
What Drives The Conductor Size
A few inputs set the radial gauge:
- Current the radial is expected to carry
- One-way length of the radial run
- Copper or aluminum conductor
- Termination temperature rating, often 75 degree C
- Bare or insulated conductor type
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
How do I size the wire for a ground radial?
Set the gauge by the current the radial carries and the run length, then read the NEC 310.16 ampacity for that conductor. Copper and aluminum give different sizes for the same load.
Does run length change the radial wire size?
Yes, longer radials add resistance, so a longer run can push you to a larger conductor. Verify the final gauge against the current NEC and your local authority having jurisdiction, since grounding rules can be amended locally.
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.