Ground Wire Size Chart (Equipment Grounding Conductor)
The minimum wire-type equipment grounding conductor for a circuit is set by the rating of the breaker or fuse protecting that circuit — not by the load. Find the overcurrent device rating below and read off the smallest copper or aluminum ground wire the code allows. Values per NEC 250.122 (2020 and later editions).
Minimum EGC size by overcurrent device
| Breaker / fuse rating (A) | Copper EGC (min) | Aluminum EGC (min) |
|---|---|---|
| 15 | 14 AWG | 12 AWG |
| 20 | 12 AWG | 10 AWG |
| 60 | 10 AWG | 8 AWG |
| 100 | 8 AWG | 6 AWG |
| 200 | 6 AWG | 4 AWG |
| 300 | 4 AWG | 2 AWG |
| 400 | 3 AWG | 1 AWG |
| 500 | 2 AWG | 1/0 AWG |
| 600 | 1 AWG | 2/0 AWG |
| 800 | 1/0 AWG | 3/0 AWG |
| 1,000 | 2/0 AWG | 4/0 AWG |
| 1,200 | 3/0 AWG | 250 kcmil |
| 1,600 | 4/0 AWG | 350 kcmil |
| 2,000 | 250 kcmil | 400 kcmil |
| 2,500 | 350 kcmil | 600 kcmil |
| 3,000 | 400 kcmil | 600 kcmil |
| 4,000 | 500 kcmil | 750 kcmil |
| 5,000 | 700 kcmil | 1250 kcmil |
| 6,000 | 800 kcmil | 1250 kcmil |
What this chart is (and is not)
This is the equipment grounding conductor (EGC) — the green or bare wire run with the circuit that gives fault current a low-impedance path back to the source so the breaker trips. It is not the grounded (neutral) conductor, and it is not the grounding electrode conductor that ties the service to the ground rods or building steel — that one is sized from the service-entrance conductors under NEC 250.66, a different table we'll publish separately.
The sizing logic is about fault clearing, which is why the chart keys on the overcurrent device and not the load: a bigger breaker allows more fault current for longer, so it demands a heavier ground path.
The upsizing rule everyone forgets
If you increase the circuit conductors beyond what the code minimally requires — most often to tame voltage drop on a long run — NEC 250.122(B) requires the EGC to grow in proportion to the circular-mil increase. Example: a 40 A circuit wired in 8 AWG copper needs a 10 AWG copper EGC per this chart; if you upsize those conductors to 6 AWG for a 200-ft run, the EGC must be upsized by the same 26,240/16,510 ratio, which lands on 8 AWG. Run the numbers with the voltage drop calculator and take the circular mils from the wire ampacity chart.
Two ceilings keep this sane: the EGC never has to be larger than the ungrounded circuit conductors, and where the raceway itself qualifies as the grounding path (EMT, IMC, RMC in sound condition), a wire-type EGC may not be required at all — though many specs demand one anyway.
Common questions
What size ground wire do I need for a 200 amp service or feeder?
For a circuit protected at 200 A, the minimum equipment grounding conductor is 6 AWG copper or 4 AWG aluminum (values per NEC 250.122). Note this is the EGC — the wire-type grounding conductor run with the circuit — not the grounding electrode conductor to the ground rod or water pipe, which is sized separately under NEC 250.66.
Is the ground wire the same size as the circuit conductors?
Usually not. The EGC only carries current during a fault, so it can be smaller than the circuit conductors — a 100 A circuit with 3 AWG copper conductors needs only an 8 AWG copper EGC. Two limits apply: it never needs to be larger than the circuit conductors, and if you upsize the circuit conductors (for example for voltage drop), NEC 250.122(B) requires the EGC to be upsized proportionally.
Which breaker rating do I use when the breaker is oversized for a motor?
Motor circuits are the classic exception: the branch-circuit device (which may be sized at several times motor full-load current for starting inrush) is still the rating you take into this chart per 250.122, but 250.122(D) lets the EGC be sized from the motor overload rating instead in some cases. When in doubt, size from the OCPD rating shown on this chart — it is never too small.
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