An approach using a combination of well known circuit principles, is used to convert the impedance matrixdetermined for three phase, single lamination/phase busway -to industry specified 'average' impedance values as specified by the National Electrical Manufacturers Association (NEMA). This paper details how this approach can be used to predict 'average' busway impedance with reasonable accuracy, and therefore help to reduce the number of physical tests and related costs in the design process. Four cases are provided for validation purposes. The results show good correlation with published data.