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⚡ Tool

Cable Size Calculator

Enter the load current, voltage, one-way run length and allowable voltage drop to estimate the minimum copper cable cross-section by voltage drop, then check ampacity against the wiring regulations.

Result

Min cross-section (voltage drop)–
Nearest standard size–

Planning estimate from the single-phase voltage-drop formula (copper) — confirm the final design with a qualified engineer and local code.

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🧮 House Material Calculator →🚰 Pipe Size Calculator →🔌 Electrical Load Calculator →

FAQ

How is cable size determined?
This tool sizes by voltage drop for a single-phase copper run: minimum area = 2 × current × length × resistivity ÷ allowed drop. The chosen cable must ALSO satisfy the current-carrying capacity (ampacity) tables and any derating in the wiring regulations.
Does this replace the wiring regulations?
No. It gives a planning-level voltage-drop size only. Final selection must check ampacity, grouping, ambient temperature and protection with the applicable regulations and a qualified electrician.

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