A display device is provided including a timing controller configured to output a test image signal, a data driver configured to output a plurality of data voltages corresponding to the test image signal; and a display panel configured to display a test image corresponding to the data voltages, wherein the timing controller includes a first processor configured to output the test image signal in response to a test signal, and a second processor configured to receive luminance information of the test image, correct a predetermined reference gamma voltage corresponding to the test image with reference to the received luminance information, and output the test signal, which corresponds to the reference gamma voltage, to the first processor.