How To Calculate Cable Sizes (2026)

PVC-insulated copper, clipped to wall (method C), ambient 35°C, no grouping, length 40m.

References: IEC 60364-5-52, BS 7671 (UK), NEC Article 310 (US), AS/NZS 3008 (Australia). how to calculate cable sizes

Where ( I_z ) = derated cable ampacity. Load: 5 kW heater, 230V AC, power factor = 1. ( I_b = 5000 / 230 = 21.74 A ) PVC-insulated copper, clipped to wall (method C), ambient

[ I_z \geq I_b ]