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ALL CABLINGWired & Wireless

Working tools

Electrician's calculators

Nine practical calculators Paul uses on the road, rebuilt from first principles against BS 7671:2018+A4:2026. Clean inputs, honest maths, and a plain reference to the regulation or table behind every result. Free to use — no sign-up, no tracking.

Guidance only. Results must be verified by a competent person against BS 7671, manufacturer data and site conditions. All Cabling Limited accepts no liability for any loss, damage, injury or non-compliance arising from use of these tools. By using them you accept these terms.

Amendment currency

Reviewed against Amendment 3:2024 (31 July 2024 — bidirectional protective devices where an additional source such as PV or battery storage is present) and Amendment 4:2026 (published 15 April 2026, mandatory 15 October 2026 — introduces Chapter 57 for battery storage, revises Section 722 for EV chargers, and adds PoE/ICT earthing requirements).

Voltage drop limits (3% lighting / 5% other), cable current-carrying capacity tables, adiabatic k values and maximum Zs Tables 41.2 / 41.3 / 41.4 are unchanged in A4 — every calculator below remains valid. Chapter 57 (BESS) and Section 722 (EV) are design/installation regulations rather than calculation inputs; refer to the Orange Book and manufacturer instructions for those.