The Technical paper present the mathematical model that predicts the radiator thermal performance curves for different airflow and coolant flow. This model was modeled using the signal library of AMEsim software. The model accepts the inputs of radiator parameters such as Air flow, Ambient temperature, Core size, Tube pitch, FPDM, No of rows, Louver pitch, Fin thickness, Louver angle Tube section data, Tube thickness, Coolant lpm, Max allowable coolant temp. The output of this model is the Radiator Performance Curve. This model is quick tool to work out approximate size of radiator to start system level packaging, Hence the Product Development time can be saved in Radiator Sizing.