High-power light emitting diode (HPLED) is an emerging technology in automotive, aerospace, domestic, and industrial lighting applications. Application of HPLED in the above mentioned areas are challenging, as effective cooling is required for maximal luminous output and longer life. This chapter deals with estimation of the total luminous flux of HPLED using a mathematical model for a given heat sink configuration, and electric and thermal conditions. The parameters that are considered in this model are voltage, current, the power of HPLED, the number of the LEDs in the module, thermal parameters such as the junction temperature of LED, heat sink and fin temperature, ambient temperature, and thermal resistances. The proposed model will be helpful for designing and predicting the luminous output of LED and also arriving at optimal heat sink and fin configurations for a given design. © Springer Nature Switzerland AG 2019.