The thermal conductivity of five predominately pearlitic grades of lamellar, compacted and spheroidal graphite iron have been modelled by means of existing models based on average field approximations. The model is based on the area fraction of different constituents and the width to length ratio of the graphite. The thermal conductivity of graphite in cast iron is derived by inverse modelling. These data are used in combination with experimental thermal conductivity values for a pearlitic matrix in order to model the thermal conductivity of various cast iron grades with good agreement. The calculations are executed for cast iron from room temperature up to 500°C.