Equipment Grounding Conductor (EGC) Sizing Calculator (NEC 250.122)
Branch circuit wiring, grounding motors, sub-panels, and machinery. Sizes equipment safety ground wire for branch circuits and feeders (15A to 1200A), with automatic proportional adjustment for voltage-drop upsized conductors.
Step-by-Step Derivation ▼ Show Steps
Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.
Engineering Principles & Calculations
This calculator uses the exact mathematical relationships between Circuit Breaker Rating (Amps: 15A to 1200A), Conductor Material (Copper / Aluminum), Has Circuit Wire Been Upsized for Voltage Drop? (Yes/No) to determine Required Ground Wire Size (AWG / kcmil). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.
Sizes equipment safety ground wire for branch circuits and feeders (15A to 1200A), with automatic proportional adjustment for voltage-drop upsized conductors.
Typical Application & Industry Guidelines
Branch circuit wiring, grounding motors, sub-panels, and machinery.
Equipment Grounding Conductor (EGC) Sizing Calculator (NEC 250.122) Benchmark Lookup Table
| Rating of Overcurrent Device (Breaker) | Min Copper EGC Wire | Min Aluminum EGC Wire |
|---|---|---|
| 15 Amp Breaker | #14 AWG Copper | #12 AWG Aluminum |
| 20 Amp Breaker | #12 AWG Copper | #10 AWG Aluminum |
| 30 - 60 Amp Breaker | #10 AWG Copper | #8 AWG Aluminum |
| 100 Amp Breaker | #8 AWG Copper | #6 AWG Aluminum |
| 200 Amp Breaker | #6 AWG Copper | #4 AWG Aluminum |
| 300 Amp Breaker | #4 AWG Copper | #2 AWG Aluminum |
| 400 Amp Breaker | #3 AWG Copper | #1 AWG Aluminum |