Equipment Grounding Conductor Calculator
Look up a minimum equipment grounding conductor size from overcurrent-device rating, material, phase-conductor upsizing, and parallel raceway count.
Circuit and conductor details
Enter the device rating in amperes.
Size required before design-related upsizing.
Assumes the same phase-conductor size in each raceway. Each raceway gets a separate EGC.
Each parallel raceway requires a separate EGC sized for the entered phase-conductor size; do not divide the table size by the number of raceways.
About this calculator
Use the overcurrent-device rating to find the baseline equipment grounding conductor size in NEC Table 250.122(A). The calculator can also apply a proportional size increase when ungrounded conductors have been increased for voltage drop or another design reason.
For parallel raceways with matching phase-conductor sizes, it returns the minimum size for each raceway separately. It does not divide the grounding conductor size across the raceways.
Method and assumptions
The table lookup selects the first overcurrent-device rating that is not less than the entered device rating. For design-related upsizing, the required grounding conductor area is increased in the same ratio as the ungrounded conductor circular-mil area. Upsizing solely for ambient-temperature or conductor-count correction is excluded from this proportional step.
The result is limited to the listed table sizes and common copper, aluminum, and copper-clad aluminum selections. Separate provisions can apply to parallel conductors, multiple circuits, flexible cords, equipment types, and other installations. Verify the exact adopted NEC requirements and the authority having jurisdiction.
FAQs
Which overcurrent-device rating should I enter?
Enter the rating of the overcurrent device protecting the circuit. This calculator does not determine or recommend that rating.
When does phase-conductor upsizing increase the equipment grounding conductor?
The proportional increase applies when ungrounded conductors are increased in size for reasons such as voltage drop or other design considerations. An increase made only to compensate for ambient temperature or conductor-count adjustment does not by itself trigger this proportional increase.
Do I divide the equipment grounding conductor size across parallel raceways?
No. Where parallel conductors are installed in separate raceways, each raceway needs its own equipment grounding conductor sized for the conductors in that raceway. Do not divide the table size by the number of raceways. Enter separate calculations if phase-conductor sizes differ by raceway.
Does this select the complete grounding and bonding system?
No. This tool looks up an equipment grounding conductor size for the stated inputs. It does not size grounding electrode conductors or determine every bonding, parallel-circuit, or equipment-specific requirement.
Sources
- 2026 NFPA 70 (NEC), Section 250.122 and Table 250.122(A)
- Verify the edition adopted by the authority having jurisdiction, including local amendments.