WireGaugeCalc Free calculator · NEC cited · works offline
Ground Wire Size Calculator
Ground wire size calculator is quick with WireGaugeCalc, since you enter the breaker or fuse rating and read the minimum grounding conductor size.
The grounding conductor sizing calculator pulls its values from the NEC table that matches device rating to copper and aluminum ground sizes.
You get a code-based answer in seconds instead of flipping pages on the truck.
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 this ground size calculator works
Your equipment grounding conductor is keyed to the rating of the overcurrent device, so the tool asks for that number first.
The ground wire calculator then lists both the copper and aluminum sizes, since the same protection often allows a smaller copper conductor.
If your phase conductors were enlarged for voltage drop, the result scales the ground up to keep it proportional.
What the groundwire size calculator needs from you
A correct ground size comes from these inputs:
- Overcurrent device rating in amps
- Conductor material, copper or aluminum
- Whether phase conductors were upsized for voltage drop
- Number of parallel raceways on the circuit
- Equipment termination temperature column
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
Does this ground wire size calculator use the load or the breaker rating?
It uses the rating of the overcurrent device protecting the circuit, since the NEC sizes the equipment grounding conductor from that value. The calculated load does not set the ground size directly.
Why does the calculator show different copper and aluminum sizes?
Copper carries more current per size than aluminum, so the NEC lists a smaller copper conductor for the same protection. Verify the final size against the current NEC and your local authority having jurisdiction before you order wire.
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.