A display device includes a display unit, a common voltage measuring unit, and a signal controller. The display unit include a plurality of pixels, each including a liquid crystal capacitor including a terminal coupled to a common electrode to receive a common voltage and a pixel electrode to receive a gray scale voltage. The common voltage measuring unit measures a change in the common voltage resulting from a coupling between the common electrode and the pixel electrode when a test image including a specific pattern is output to the display unit. The signal controller detects a level of a residual DC voltage of a liquid crystal layer between the common electrode and pixel electrode based on a measured value of the common voltage.