A micro heat flux sensor which can measure the thermal energy transfer per unit area has been designed, fabricated, and calibrated in a convective environment. The sensor which is based on a circular foil gage is composed of thermal paths and a thermopile. The thermal path is made in a LIGA-like process of SU-8 high aspect ratio microstructures and electroplated copper layers. The thermopile, a series of thermocouples, is used to amplify the output signal as a thermometer. When the sensor is placed on a high-temperature wall, heat flux from the wall flows through thermal paths and drains out to the environment, producing a temperature difference along its paths. Heat flux is obtained by calibrating this temperature difference in the thermopile of Ni-Cr or Al-Chromel pairs. The sensitivity of the heat flux sensor of Ni-Cr and Al-Chromel pairs is in the range of 0.1-2.0 and 0.4-2.0 muV mW(-1) cm(-2), respectively, in the heat flux range of 0-180 mW cm(-2).