An organic light emitting display device includes a pixel unit including data lines, a data driving unit providing data signals corresponding to first and second data to the data lines, a timing controlling unit controlling the data driving unit and supplying the first data from the outside, and a power supply for the pixel, data driving, and timing controlling units. A converting unit may receive the first data from the timing controlling unit, convert the first data into the second data, and transmit the converted second data to the data driving unit. When the first data supplied from the timing controlling unit has a digital bit corresponding to one of a first range for displaying white-related colors and a second range for displaying black-related colors, the converting unit converts the first data into the second data having a digital bit corresponding to one of the second and first ranges, respectively.