Bs7671 Cable Sizing May 2026

For any electrical installation operating in the UK, compliance with BS 7671 (IET Wiring Regulations) is not optional—it is a legal benchmark under the Electricity at Work Regulations 1989. At the heart of this compliance lies a process often misunderstood as simple table-lookup: cable sizing .

[ S = \frac\sqrtI^2 tk ]

For a final circuit: