Ground wire size calculator based on NEC 250.122 Standard
Does this calculator work for service entrance? Of course not. This is for equipment grounding (EGC) based on breaker size (Table NEC 250.122), not for service grounding (Table 250.66).
⏚ Grounding Size Calculator
Based on NEC Table 250.122 (Safety Standards)
Based on NEC 250.122 for Copper.
*Metric (mm²) values are approximate conversions for reference.
What is grounding in electrical?
Grounding or earthing in the engineering is the connection of an electrical system to the soil (earth).
It creates a direct and low resistance path for excess electricity to dissipate safely into the ground, rather than passing through a person or sensitive equipment. This can prevent the electric shock to harm people and damaging equipment.
What is ground wire size chart?
Ground wire size refers to the physical thickness of the minimum cable size for safety that connect electrical equipment to the earth (ground). This ground wire usually have the color yellow & green.
Ground wire size table base on NEC
There is no formula in determining the ground wire size. We should look at the NEC table and NEC chart as the base on determining the ground wire size.
Table: NEC 250.122 - Minimum Ground Wire Size
Use this table to quickly find the Equipment Grounding Conductor (EGC) size based on your circuit breaker rating.
| Breaker / Fuse Rating (Amps) | Copper Wire Size (Cu) | Aluminum Wire Size (Al) |
|---|---|---|
| 15 Amps | 14 AWG | 12 AWG |
| 20 Amps | 12 AWG | 10 AWG |
| 60 Amps | 10 AWG | 8 AWG |
| 100 Amps | 8 AWG | 6 AWG |
| 200 Amps | 6 AWG | 4 AWG |
| 300 Amps | 4 AWG | 2 AWG |
| 400 Amps | 3 AWG | 1 AWG |
| 500 Amps | 2 AWG | 1/0 AWG |
| 600 Amps | 1 AWG | 2/0 AWG |
| 800 Amps | 1/0 AWG | 3/0 AWG |
| 1000 Amps | 2/0 AWG | 4/0 AWG |
Nec based ground wire size chart
NEC Table 250.122 Cheat Sheet
Minimum Size of Equipment Grounding Conductors| Breaker Rating (Overcurrent Device) |
Copper Wire (Most Common) |
Aluminum Wire (Aluminum/CCA) |
|---|---|---|
| 15 Amps | 14 AWG | 12 AWG |
| 20 Amps | 12 AWG | 10 AWG |
| 30 - 60 Amps | 10 AWG | 8 AWG |
| 100 Amps | 8 AWG | 6 AWG |
| 200 Amps | 6 AWG | 4 AWG |
| 300 Amps | 4 AWG | 2 AWG |
| 400 Amps | 3 AWG | 1 AWG |
| 500 Amps | 2 AWG | 1/0 AWG |
| 600 Amps | 1 AWG | 2/0 AWG |
| 800 Amps | 1/0 AWG | 3/0 AWG |
| 1000 Amps | 2/0 AWG | 4/0 AWG |
| 1200 Amps | 3/0 AWG | 250 kcmil |
| 1600 Amps | 4/0 AWG | 350 kcmil |
| 2000 Amps | 250 kcmil | 400 kcmil |
Understanding NEC 250.122
We talked much about NEC. What is it? In the world of electrical engineering, determining the size of the equipment grounding conductor (EGC) correctly is a MUST. It is very critical for safety. The contractors / installers / applicators must ensure that if a fault occurs, the breaker must immediately trip, otherwise it will be very dangerous and causes electric shock.
Now, engpocket friends already know how to determine the ground wire size, we are wonder, do you eager to use our watts to amps calculator and converting 3 phase and single phase on this link? Check it out