WireGaugeCalc Free calculator · NEC cited · works offline
Ground Wire Size For 100 Amp Service
Ground wire size for 100 amp service is quick with WireGaugeCalc, since you pick the service amperage and conductor material and it returns the size.
The calculator reads the NEC grounding tables for you, so it separates the grounding electrode conductor from the equipment grounding conductor.
You get a clear number to wire the panel and pass inspection without flipping through the code book.
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.
100 Amp Service Ground Size, Read Straight From The Code
The grounding electrode conductor for a 100 amp service is commonly #8 copper or #6 copper, since the size follows NEC Table 250.66 by the service conductor size.
The equipment grounding conductor inside the panel is sized by NEC Table 250.122 against the 100 amp overcurrent device, so it differs from the electrode conductor.
WireGaugeCalc shows both numbers at once, so you do not mix up the two grounds on the job.
100 Amp Sub Panel Ground Wire Size And Service Entrance
A few inputs cover the grounds you need for a 100 amp service or feeder:
- Service amperage set to 100 amps
- Copper or aluminum conductor material
- Grounding electrode conductor per NEC 250.66
- Equipment grounding conductor per NEC 250.122
- Separate neutral and ground for a 100 amp sub panel
- Ground wire size for a 100 amp entrance and feeder runs
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 size of ground wire is needed for 100 amp service?
The grounding electrode conductor is often #8 or #6 copper to the ground rods, while the equipment grounding conductor is usually #8 copper. Verify the exact size against the current NEC and your local authority having jurisdiction, since rod versus rebar electrodes can change the answer.
Is the ground wire size different for a 100 amp sub panel?
Yes, a sub panel uses an equipment grounding conductor sized by NEC 250.122, and the neutral and ground must stay separated at the sub panel.
Can I use aluminum for the 100 amp service ground?
Aluminum is allowed in many cases and uses a larger size than copper. The calculator gives the aluminum number so you can compare both materials.
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.