NEC Table 250.122 EGC Sizing
Minimum equipment grounding conductor size from NEC Table 250.122, listed by the rating of the overcurrent device protecting the circuit, from 15 A through 2000 A, in copper and aluminum.
| OCPD rating up to | Copper | Aluminum |
|---|---|---|
| 15 A | 14 AWG | 12 AWG |
| 20 A | 12 AWG | 10 AWG |
| 30 A | 10 AWG | 8 AWG |
| 40 A | 10 AWG | 8 AWG |
| 60 A | 10 AWG | 8 AWG |
| 100 A | 8 AWG | 6 AWG |
| 200 A | 6 AWG | 4 AWG |
| 300 A | 4 AWG | 2 AWG |
| 400 A | 3 AWG | 1 AWG |
| 500 A | 2 AWG | 1/0 AWG |
| 600 A | 1 AWG | 2/0 AWG |
| 800 A | 1/0 AWG | 3/0 AWG |
| 1000 A | 2/0 AWG | 4/0 AWG |
| 1200 A | 3/0 AWG | 250 kcmil |
| 1600 A | 4/0 AWG | 350 kcmil |
| 2000 A | 250 kcmil | 400 kcmil |
NEC Table 250.122. Minimum equipment grounding conductor by the rating or setting of the overcurrent device ahead of the circuit. Upsized phase conductors require a proportionally larger EGC · 250.122(B). Parallel runs in separate raceways need a full-size EGC in every raceway · 250.122(F).
How to use this table
Start from the breaker or fuse, not the wire. Find the first row whose rating is at or above your overcurrent device and read the minimum EGC for your material. The EGC is the fault-clearing path that runs with the circuit conductors; its whole job is to carry enough fault current to open that device fast.
When the table row is not enough
If the ungrounded conductors were upsized for any reason, voltage drop being the usual one, the EGC must grow by at least the same ratio of circular-mil areas · 250.122(B). A run sized up two positions for a long feeder drags its EGC up with it, and the table row alone is no longer compliant. For parallel conductors in separate raceways or cables, each raceway gets a full-size EGC sized from this table; the EGC is never split between raceways · 250.122(F).
Related sizing
This table covers equipment grounding. The conductor to the grounding electrode system is sized from the service conductors instead, per Table 250.66. For the circuit conductors the device protects, start from the Table 310.16 ampacity chart or run the free wire size calculator. The JobVolt app's grounding calculator applies the upsizing ratio and the parallel-raceway rule automatically and cites each step.
This table lives in the app, offline.
JobVolt opens the right NEC table from any result with your row highlighted, works with no signal, and turns calculations into inspector-ready PDF submittals on your letterhead.
