WireGaugeCalc Free calculator · NEC cited · works offline
Equipment Grounding Conductor Size
Equipment grounding conductor size is simple with WireGaugeCalc, since you enter the circuit's overcurrent device rating and read the required ground size.
The calculator follows the NEC sizing rule that ties the grounding conductor to the breaker or fuse ahead of the circuit.
You walk away with the right copper or aluminum size before you cut the wire.
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.
Electrical conductor grounding sizing tied to the breaker
The equipment grounding conductor is sized from the rating of the overcurrent device protecting the circuit, so a larger breaker calls for a larger ground.
WireGaugeCalc reads that rating and returns the minimum ground size for both copper and aluminum, since the two metals are listed separately.
When you upsize the phase conductors for voltage drop, the ground may need to grow in proportion, and the tool accounts for that case.
Inputs for sizing ground wire per NEC
The grounding conductor size depends on these factors:
- Overcurrent device rating, which sets the base ground size
- Conductor material, since copper and aluminum have separate columns
- Upsized phase conductors, which can require a proportionally larger ground
- Parallel runs, where each raceway needs a full-size ground
- Termination temperature rating at the equipment lugs
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 the equipment grounding conductor get larger when I upsize the phase wires?
Yes, if you increase the ungrounded conductors above the minimum for ampacity, the equipment grounding conductor must increase in the same proportion. Confirm the exact ratio against the current NEC and your local authority having jurisdiction.
Is the ground sized by the load current or by the breaker?
It is sized by the rating of the overcurrent device protecting the circuit, not by the calculated load. WireGaugeCalc uses that device rating to return the minimum ground size.
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.