Earth Conductor Size Calculator
Find the minimum protective (earth) conductor size for a circuit from its phase conductor size, using the standard relationship in IS 732 / IEC 60364. This sizes the circuit’s earth conductor; the main earthing conductor to the electrode and the earthing design itself are separate — and, like everything here, are set by a licensed electrician to IS 3043.
sizes in sq mm (copper)
The rule
- S ≤ 16 → earth = S (same as phase)
- 16 < S ≤ 35 → earth = 16
- S > 35 → earth = S ÷ 2
For a 4 sq mm phase conductor, the protective conductor is equal to the phase conductor.
This is the circuit protective conductor (the earth wire run with the circuit). It is a minimum from the simplified rule; a full design may use the adiabatic calculation and can differ. The main earthing conductor to the earth electrode, and the earthing system design, are separate matters governed by IS 3043.
Indicative only. This uses the standard simplified size relationship for a same-material protective conductor and does not perform the full adiabatic calculation or account for every installation condition. It sizes the circuit’s earth conductor only — not the main earthing conductor or the earth electrode. All earthing and conductor sizing must be designed and verified by a licensed electrician to IS 732 and IS 3043.
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