When to use this: at design or rough-in to size grounding conductors. Use the GEC mode at the service for the connection to the grounding electrode system, and the EGC mode for every branch circuit. Pair with the NEC Wire Size Calculator for the phase conductor pick.
Grounding Conductor Sizer
Returns the GEC per NEC Table 250.66 (sized from the service-entrance conductor) or the EGC per NEC Table 250.122 (sized from the branch-circuit OCPD).
Result
Reference table—
Required minimum size—
Notes—
Last reviewed: April 2026 (NEC 2023). For installation, follow the actual NEC table – this is a planning aid.
Tools we used or recommend for this work: a Klein lug-crimp tool for grounding terminations, a green-bonded grounding bushing, and an irreversible compression connector kit (Burndy / Ilsco) for direct-burial GEC splices. Links may be affiliate-tagged where the brand has a program.
