A system for compensating for gamma data is provided comprising a display panel including at least one feedback line connected to at least one pixel, a gray voltage generator generating a reference gray voltage based on first gamma data, a data driver generating a data voltage based on the reference gray voltage and applying the generated data voltage to a data line, a multiplexer receiving at least one feedback voltage from the at least one feedback line and selecting a feedback voltage from the received at least one feedback voltage and outputting the selected feedback voltage, an A/D converter converting the selected feedback voltage into feedback data, and a signal controller storing the feedback data as feedback gamma data for the entire grays and compensating for the first gamma data based on the feedback gamma data.