Grounding Conductor Size Chart — NEC 250.122 & 250.66
Minimum equipment grounding conductor size by overcurrent device rating, and grounding electrode conductor size by service conductor size.
Copper ground wire size: 15 A → 14 AWG · 20 A → 12 AWG · 30–60 A → 10 AWG · 100 A → 8 AWG · 200 A → 6 AWG · 400 A → 3 AWG · 600 A → 1 AWG · 800 A → 1/0 · 1000 A → 2/0 · 1200 A → 3/0.
Equipment grounding conductor — Table 250.122
Find the rating of the breaker or fuse protecting the circuit. If it falls between two rows, use the next higher row.
| Breaker or fuse rating, not exceeding | Copper EGC | Aluminum or copper-clad aluminum EGC |
|---|---|---|
| 15 A | 14 AWG | 12 AWG |
| 20 A | 12 AWG | 10 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 |
| 2500 A | 350 kcmil | 600 kcmil |
| 3000 A | 400 kcmil | 600 kcmil |
| 4000 A | 500 kcmil | 750 kcmil |
| 5000 A | 700 kcmil | 1250 kcmil |
| 6000 A | 800 kcmil | 1250 kcmil |
Rules that go with the table
- Upsizing: if circuit conductors are increased for voltage drop, increase the EGC proportionally (250.122(B)).
- Multiple circuits in one raceway: a single EGC sized for the largest overcurrent device is permitted (250.122(C)).
- Motor circuits: size from the branch-circuit short-circuit and ground-fault device; where that is an instantaneous-trip breaker or motor short-circuit protector, 250.122(D) permits sizing from the dual-element fuse rating instead.
- Parallel runs: a full-size EGC in every raceway (250.122(F)).
- Metal raceways such as EMT, IMC and RMC qualify as the equipment grounding conductor themselves (250.118); a wire-type EGC is then optional unless the specification calls for one.
Grounding electrode conductor — Table 250.66
Sized from the largest ungrounded service-entrance conductor, or the equivalent area of parallel sets.
| Largest ungrounded service-entrance conductor | Grounding electrode conductor | ||
|---|---|---|---|
| Copper | Aluminum | Copper | Aluminum |
| 2 AWG or smaller | 1/0 AWG or smaller | 8 AWG | 6 AWG |
| 1 or 1/0 AWG | 2/0 or 3/0 AWG | 6 AWG | 4 AWG |
| 2/0 or 3/0 AWG | 4/0 AWG or 250 kcmil | 4 AWG | 2 AWG |
| Over 3/0 AWG – 350 kcmil | Over 250 – 500 kcmil | 2 AWG | 1/0 AWG |
| Over 350 – 600 kcmil | Over 500 – 900 kcmil | 1/0 AWG | 3/0 AWG |
| Over 600 – 1100 kcmil | Over 900 – 1750 kcmil | 2/0 AWG | 4/0 AWG |
| Over 1100 kcmil | Over 1750 kcmil | 3/0 AWG | 250 kcmil |
Maximum sizes by electrode type: the GEC need not be larger than 6 AWG copper (4 AWG aluminum) where it connects only to rod, pipe or plate electrodes, nor larger than 4 AWG copper where it connects only to a concrete-encased electrode (Ufer), whatever the service size.
Frequently asked questions
What size ground wire do I need for a 100 amp circuit?
8 AWG copper or 6 AWG aluminum. The equipment grounding conductor is sized from the rating of the breaker or fuse ahead of the circuit, not from the size of the circuit conductors.
What size ground for a 200 amp panel?
A 200 A feeder needs a 6 AWG copper or 4 AWG aluminum equipment grounding conductor. A 200 A service is different: its grounding electrode conductor is sized from Table 250.66 — 4 AWG copper for 2/0 or 3/0 copper service conductors — and need not be larger than 6 AWG copper where it runs only to ground rods.
What size ground wire for 20, 30, 40, 50 and 60 amp circuits?
12 AWG copper for 20 A, and 10 AWG copper for anything over 20 A up to 60 A. So 30, 40, 50 and 60 A circuits all take a 10 AWG copper ground.
Do I have to upsize the ground if I upsize the wire for voltage drop?
Yes. If the ungrounded conductors are increased in size for voltage drop, the equipment grounding conductor must be increased in the same proportion by circular-mil area (250.122(B)). Going from 12 AWG to 10 AWG hots on a 20 A circuit means a 10 AWG ground.
Does the ground ever need to be larger than the circuit conductors?
No. The equipment grounding conductor is never required to be larger than the circuit conductors supplying the equipment.
How are grounds sized for parallel conduits?
Each raceway needs its own equipment grounding conductor, and each one is sized in full from the overcurrent device rating — not divided by the number of parallel runs.
What is the difference between an EGC and a GEC?
The equipment grounding conductor (EGC) runs with every circuit and bonds metal equipment back to the source so a fault trips the breaker; it is sized from Table 250.122. The grounding electrode conductor (GEC) connects the service to earth — ground rods, water pipe, concrete-encased electrode — and is sized from Table 250.66.
NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.