A display device includes a plurality of pixels grouped into blocks divided into block rows extending in a first direction and arranged in a second direction, wherein each block includes two or more pixels connected to a first power source line, and each pixel is assigned with a grayscale value in a range of grayscale values that is divided into a plurality of grayscale sections; and a first power source voltage adjuster selecting a reference block row, and determining a magnitude of a first power source voltage supplied to the first power source line based on a number of blocks in the reference block row having a grayscale section that is same as a maximum grayscale section of the reference block row. The maximum grayscale section corresponds to a grayscale section that includes a largest grayscale value having a grayscale value ratio greater than a minimum ratio.