Busbar size calculator

This is a first estimate, not a rating. A busbar has no calculable rating in the standard: IEC 61439 proves the temperature rise with a type test, and manufacturer data always wins over any figure on this page, which is why the density override exists. The estimate carries a current density of 1.6 A/mm² on copper and 1.0 on aluminium in still air, then applies the factors named in the result. Losses use DC resistance only, so they read optimistic on thick bars, where skin effect pushes current to the surface; at 50 Hz the skin depth in copper is about 9.3 mm, which is why thin wide bars beat thick square ones. Short-circuit electromagnetic forces and the bracing they demand are out of scope entirely. Aluminium needs roughly 1.6 times the cross-section of copper for the same job at about a third of the weight, and the real difficulty is jointing, not the bar.