Grounding Conductor Size Calculator

Ground is the safety net of the installation - the path that turns a faulted live part into a tripped circuit instead of a shocking one. But the net is only as strong as its thinnest strand, and the thinnest strand is the grounding conductor.

Grounding Conductor Size Calculator estimates the minimum protective/earthing conductor size two ways: the NEC table method keyed to the protection rating, and the IEC /2-principle from the phase cross-section.

It is a planning aid. Final selection follows the code edition and earthing system (TT, TN, IT) in force.

• Two methods: NEC table lookup or IEC /2 rule.
• Phase conductor: Enter AWG or mm².
• Protection rating: Breaker/fuse in amps for NEC.
• Material: Copper or aluminium.
• Both results: Show NEC and IEC together.
• Standard sizes: Nearest conductor bumped up.
• Export: Copy or download as text, CSV or JSON.

1. Pick the method: NEC (protective device) or IEC (phase cross-section).
2. Enter the breaker/fuse rating or the phase mm²/AWG.
3. Choose the material.
4. Select the standard you will install to.
5. Read the minimum grounding conductor size.
6. Confirm with the code table in force.

Example 1 — NEC. A 60 A circuit: Table 250.122 calls 10 AWG copper equipment grounding conductor.

Example 2 — IEC. A 25 mm² phase conductor protected to 6 mm² minimum: /2 gives 16 mm².

Example 3 — Both. A 40 A branch with 10 mm² phase: NEC gives 10 AWG, IEC /2 rounds to 6 mm².

• Two conventions: NEC and IEC results side by side.
• Simple inputs: Breaker amps or phase cross-section.
• Immediate answer: Standard size chosen for you.
• Material aware: Adjusts for aluminium.
• Private: No uploads, no accounts, no logging.