Grounding Electrode Conductor Size Calculator
Look up a grounding electrode conductor size from the largest ungrounded service conductor, conductor material, and electrode connection.
Service and electrode details
Supported sizes: 8 AWG, 6 AWG, 4 AWG, 2 AWG, 1 AWG, 1/0 AWG, 2/0 AWG, 3/0 AWG, 4/0 AWG, 250 kcmil.
About this calculator
This lookup applies 2026 NEC Table 250.66 to the selected service-conductor material and size. It can also apply the listed exception for a sole rod, pipe, or plate connection; a sole concrete-encased connection; or a ground-ring connection with a known ring conductor size.
The output is a minimum size for the stated connection. It does not design the complete grounding electrode system or determine all conductor routing, bonding, parallel-service, or equipment requirements.
Method and assumptions
The table range is selected from the largest ungrounded service conductor or equivalent area for parallel conductors. The result uses the Table 250.66 conductor-material column selected for the grounding electrode conductor.
An electrode-specific provision applies only when the grounding electrode conductor ends at that electrode type and does not continue to another electrode requiring a larger conductor. Ground-ring sizing uses the installed ring-conductor size entered above. Verify conductor protection, material contact restrictions, connections, local adoption, and amendments.
FAQs
Which service conductor size should I enter?
Enter the largest ungrounded service-entrance conductor. For parallel conductors, use their combined circular-mil area per phase under Table 250.66. Multiple service sets and installations without service-entrance conductors have additional rules.
When can I use an electrode-specific size provision?
The provisions for rod, pipe, plate, concrete-encased, or ground-ring connections apply only when that grounding electrode conductor does not continue to other electrode types that require a larger size.
Why does the ground-ring option ask for the ring conductor size?
For a grounding electrode conductor that ends at the ground ring, Section 250.66(C) limits it to no larger than the ring conductor. The ground-ring conductor itself has a separate minimum-size requirement.
Can I use aluminum for the grounding electrode conductor?
Aluminum has restrictions on contact with earth, concrete, and masonry. The lookup does not determine whether the selected material and routing are permitted for your installation.
Sources
- NFPA 70 (NEC), 2026 edition, Section 250.66, Table 250.66, and subsections 250.66(A) through (C)
- Confirm the edition adopted by the authority having jurisdiction, including local amendments.