NEC Table 250.122
Ground Wire Size Chart (NEC 250.122)
Minimum equipment grounding conductor (EGC) size by overcurrent device rating, straight from NEC Table 250.122. Size the ground by the breaker, not the load.
NEC 250.122 EGC Size Chart (Copper)
| Overcurrent device rating (A) | Copper EGC (AWG / kcmil) |
|---|---|
| 15 | 14 |
| 20 | 12 |
| 30 | 10 |
| 40 | 10 |
| 50 | 10 |
| 60 | 10 |
| 100 | 8 |
| 200 | 6 |
| 300 | 4 |
| 400 | 3 |
| 500 | 2 |
| 600 | 1 |
| 800 | 1/0 |
| 1000 | 2/0 |
| 1200 | 3/0 |
| 1600 | 4/0 |
| 2000 | 250 |
| 2500 | 350 |
| 3000 | 400 |
| 4000 | 500 |
| 5000 | 700 |
| 6000 | 800 |
Copper column shown. Aluminum equipment grounding conductors are larger; see the aluminum column of NEC Table 250.122. For ratings between listed rows, use the next larger row.
How to Size the Ground Wire
The rule is simpler than most conductor sizing: read NEC Table 250.122 across from the rating of the overcurrent device (breaker or fuse) protecting the circuit. A 50A breaker uses #10 copper even though the circuit conductors are #6, because the EGC tracks the breaker, not the phase conductors.
One adjustment applies. When you upsize the ungrounded conductors for voltage drop, NEC 250.122(B) requires you to increase the EGC proportionally by the same ratio in circular mils. If you bump #6 copper up to #4 (a 41,740 to 66,360 circular-mil increase, a factor of 1.59), the #10 EGC must grow by the same 1.59 factor to at least #8.
Worked Example
60A EV charger circuit, conductors upsized for a long run
60A breaker → base EGC = #10 copper (250.122)
Conductors upsized #6 → #4 for voltage drop = 41,740 / 26,240 = 1.59x
Apply 1.59x to the #10 EGC (10,380 cmil x 1.59 = 16,504 cmil). The next size at or above that is #8 (16,510 cmil), so the upsized EGC is #8 copper per NEC 250.122(B).
Frequently Asked Questions
What size ground wire do I need for a 100 amp breaker?
The equipment grounding conductor for a 100A circuit is #8 copper per NEC Table 250.122. In aluminum the EGC is #6. The EGC is sized from the rating of the overcurrent device protecting the circuit, not from the load or the conductor size.
What size ground wire for a 50 amp breaker?
The EGC for a 50A breaker is #10 copper. NEC Table 250.122 lists 60A at #10, and any rating up to that row (30A, 40A, 50A) uses the same #10 copper. In aluminum it is #8.
What size ground wire for a 20 amp circuit?
The EGC for a 20A circuit is #12 copper per NEC 250.122, which is why 12-2 nonmetallic cable includes a #12 or bare equivalent ground. A 15A circuit uses #14 copper.
What size ground for a 200 amp service or feeder?
For a 200A overcurrent device the EGC is #6 copper or #4 aluminum per NEC 250.122. Note this is the equipment grounding conductor. The grounding electrode conductor for a 200A service is a separate calculation under NEC 250.66 (typically #4 copper to a ground rod, or larger to other electrodes).
Does the ground wire size depend on the breaker or the wire size?
The EGC is sized from the overcurrent device rating, per NEC Table 250.122. The one exception: if you upsize the ungrounded conductors for voltage drop, you must increase the EGC proportionally by the same ratio in circular mils, per NEC 250.122(B).
Is the equipment grounding conductor the same as the grounding electrode conductor?
No. The equipment grounding conductor (EGC) bonds equipment back to the source and is sized by NEC 250.122 from the breaker rating. The grounding electrode conductor (GEC) connects the system to earth (ground rod, water pipe, Ufer) and is sized by NEC 250.66 from the service conductor size. They are different conductors with different tables.
Related Calculators & Charts
Wire Size Calculator
Size the ungrounded conductors for load, distance, and derating, then the EGC follows the breaker.
Wire Ampacity Chart (310.16)
Copper and aluminum ampacities at 60, 75, and 90°C for the phase conductors.
MCA / MOCP Breaker Calculator
Nameplate to wire, breaker, and ground for HVAC and motor loads per NEC 440.
Ground is sized. Size the conductors it rides with.
The EGC follows the breaker, but the phase conductors follow the load, distance, and derating. The wire size calculator handles all three and tells you when voltage drop forces an upsize that pulls the ground up with it.