WireGaugeCalc Free calculator · NEC cited · works offline
Grounding Conductor Size For 100 Amp
Grounding conductor size for 100 amp circuits is quick with WireGaugeCalc, since you enter the breaker rating and the conductor material to read the gauge.
The calculator pulls the equipment grounding conductor size from NEC 250.122 by overcurrent rating, so a 100 amp breaker returns the matched copper or aluminum size.
Get the ground wire number before you cut so the run passes inspection.
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.
Reading 250.122 for a ground wire size for 100 amp circuit
The equipment grounding conductor is sized by breaker rating, not by the phase conductor, so a 100 amp breaker drives the lookup.
Copper lands at 8 AWG for 100 amps, while aluminum steps up since it carries less.
When you upsize the phase conductors for voltage drop, the ground scales up too, and the tool reflects that.
What the lookup considers
The ground size depends on a few inputs:
- Overcurrent device rating of 100 amps
- Copper or aluminum grounding conductor
- NEC 250.122 base size for that rating
- Upsize factor if phase conductors are enlarged
- Separate path for a grounding electrode conductor under 250.66
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
What is the ground wire size for a 100 amp circuit in copper?
For a 100 amp overcurrent device, NEC 250.122 calls for 8 AWG copper as the equipment grounding conductor. Aluminum at the same rating is larger, and you should verify against the current NEC and your local authority having jurisdiction.
Is the grounding electrode conductor the same size?
No, the grounding electrode conductor for a service follows NEC 250.66 and is based on the service-entrance conductor size, not the breaker. They are different conductors with different tables, so do not mix them up.
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.