The busbar sizing calculator determines the required busbar dimensions based on the continuous current rating, short circuit withstand, and thermal limits for switchgear assemblies. The current rating is calculated from the conductor cross-sectional area, material (copper or aluminium), and maximum. Click Calculate to see the required area and recommended size. Full IEC Verification Enter your base parameters as in the standard method. This disables the safety factor and reveals IEC-specific inputs. This article explains how the calculator works, the standards it follows (IEC and NEC), and what factors influence. A bus bar is a strip of copper (or) aluminum metal that conducts the electricity in switchboards and also distribution equipment.