NEC Grounding Conductor Size Chart: Equipment Wire Sizing Guide

The minimum equipment grounding conductor (EGC) size is determined strictly by the rating of the overcurrent protective device (breaker or fuse), not the actual load current. For a standard 15A or 20A branch circuit, the minimum EGC is 14 AWG or 12 AWG copper, respectively. For a 200A residential feeder, you need a minimum of 6 AWG copper or 4 AWG aluminum. Sizing this wire incorrectly compromises the fault-current path, preventing the breaker from tripping during a short circuit and leaving metal enclosures energized.

Below is the complete reference data derived from NFPA 70 (National Electrical Code) Table 250.122, followed by the specific calculation rules for voltage drop upsizing and parallel runs that the base chart does not cover.

How to Read the NEC Grounding Conductor Size Chart

The chart below maps the overcurrent device rating directly to the minimum required EGC size. The values assume standard installation conditions without voltage drop upsizing. To use this table, locate your breaker size in the first column, then read across to the Copper or Aluminum column depending on your wire material.

Bookmark Quick-Jumps: 15A-20A Branch | 30A-50A Appliance | 60A-100A Subpanel | 150A-400A Main Feeder

Table 250.122 Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment

Overcurrent Device Rating (Amps)	Copper Wire (AWG/kcmil)	Aluminum Wire (AWG/kcmil)
15	14	12
20	12	10
30	10	8
40	10	8
60	10	8
100	8	6
150	6	4
200	6	4
300	4	2
400	3	1
500	2	1/0
600	1	2/0
800	1/0	3/0
1000	2/0	4/0
1200	3/0	250 kcmil

15A & 20A Branch Circuits

For standard receptacle and lighting circuits, 14 AWG copper is the absolute minimum for a 15A breaker. However, most professional electricians pull 12 AWG copper for all 15A and 20A circuits to allow for future breaker upgrades and to reduce voltage drop on long runs. If you use 12 AWG wire on a 15A breaker, your EGC is already oversized, which is fully compliant.

30A to 50A Appliance Circuits

Electric dryers (30A) and ranges (50A) require 10 AWG and 6 AWG copper EGCs, respectively. Note that older 3-wire dryer/range cords relied on the neutral as a ground; modern NEC strictly requires a 4-wire setup with a dedicated EGC matching these chart values.

60A to 100A Subpanels

When feeding a detached garage or subpanel, the EGC must be run in the same raceway or cable as the ungrounded (hot) conductors. For a 100A feeder using 3 AWG copper hots, you must pull an 8 AWG copper EGC. Never rely on a buried ground rod alone to clear a fault on a subpanel feeder.

150A to 400A Main Feeders

For large residential services or commercial feeders, aluminum is heavily utilized for the ungrounded conductors due to cost. If you are pulling 4/0 aluminum for a 200A service, your EGC must be 4 AWG aluminum or 6 AWG copper. Mixing copper EGCs with aluminum hots is common and perfectly legal, provided you use appropriate bi-metallic lugs or anti-oxidant paste where required.

Copper vs. Aluminum: Which Column Applies and How Derating Works

The most common error when using the grounding conductor size chart is misapplying the material columns or ignoring proportional upsizing rules.

Which Column Applies to Your Installation?

Use the Copper column if your EGC is bare copper, THHN, or part of a standard NM-B (Romex) cable. Use the Aluminum column only if you are pulling a dedicated insulated aluminum EGC (like XHHW-2) alongside aluminum feeder conductors in conduit. You cannot use the aluminum column if you are pulling a copper ground wire, even if your hot wires are aluminum.

How Voltage Drop Upsizing Modifies the Base Value

The chart above provides the minimum baseline. However, NEC 250.122(B) mandates that if you increase the size of your ungrounded (hot) conductors to compensate for voltage drop, you must proportionally increase the size of the EGC. The table does not calculate this for you.

Failing to upsize the ground wire when you upsize the hots means the EGC might not have sufficient cross-sectional area to carry the massive fault current long enough to trip the oversized or distant breaker, creating a severe shock hazard.

What the Grounding Conductor Size Chart Cannot Tell You

While Table 250.122 is the definitive guide for equipment grounding, it has strict boundaries. Relying on it for the wrong application will result in a failed inspection. For deeper code analysis, refer to resources like Mike Holt Enterprises or your local Authority Having Jurisdiction (AHJ).

It Does Not Cover Grounding Electrode Conductors (GEC)

The EGC connects equipment back to the panel. The GEC connects the panel itself to the earth (ground rods, metal water pipes, concrete-encased electrodes). Sizing a GEC requires an entirely different chart: NEC Table 250.66. If you are bonding a 200A service panel to a ground rod, Table 250.122 is useless; you must use Table 250.66, which dictates a 4 AWG copper GEC for a 200A service based on the size of the largest ungrounded service entrance conductor.

It Does Not Account for Parallel Conductor Runs

When feeding a 400A commercial panel using parallel sets of conductors in multiple conduits, you cannot simply split the required ground wire between the pipes. NEC 250.122(F) requires that a full-size EGC be pulled in each parallel raceway. If the chart calls for a 3 AWG copper EGC for a 400A breaker, and you run two parallel conduits, you must pull a 3 AWG copper EGC in conduit A, and another 3 AWG copper EGC in conduit B. You cannot pull two 8 AWG wires and parallel them to equal a 3 AWG.

It Does Not Override the 'Next Size Up' Rule for Non-Standard Breakers

If your calculated load requires a 125A breaker (a non-standard size in many residential panels, though common in commercial), you must look at the chart for the next standard size up. You would use the 150A row, requiring a 6 AWG copper EGC, rather than interpolating between the 100A and 150A rows.