A flicker quantification system includes a display device driven in units of reference periods having a first frame for writing data and at least one second frame for holding data. A luminance measurer generates luminance data by measuring a luminance of a display during the reference period. A voltage measurer measures a voltage of a photo sensor corresponding to light emitted. First voltage data representing an accumulation amount of voltage during the first frame and second voltage data representing an accumulation amount of voltage during the at least one second frame is generated. A processor calculates a flicker index value representing a ratio of a measured luminance difference to a just noticeable difference, based on the luminance data, the first voltage data, and the second voltage data. The measured luminance difference may represent the difference between a luminance during the first frame and a luminance during the second frame.